Forensic Science:

Answer one of the below questions that has not been answered by anyone else, and then respond to submissions from at least two classmates

Option 1: List and describe the general features of bloodstain formation.

Option 2. A criminalist studying a dyed sample hair notices that the dyed color ends about 1.5 centimeters from the tip of the hair. Approximately how many weeks before the examination was the hair dyed? Explain your answer.

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Option 3. Following are descriptions of several hairs. Based on these descriptions, indicate the likely race of the person from whom the hair originated.
a. Evenly distributed, fine pigmentation.
b. Continuous medullation.
c. Dense, uneven pigmentation.
d. Wavy with a round cross-section.

Option 4. Criminalist Pete Evett is collecting fiber evidence from a murder scene. He notices fibers on the victim’s shirt and trousers, so he places both of these items of clothing in a plastic bag. He also sees fibers on a sheet near the victim, so he balls up the sheet and places it in as separate plastic bag. Noticing fibers adhering to the windowsill from which the attacker gained entrance, Pete carefully removes it with his fingers and places it in a regular envelope. What mistakes, if any, did Pete make while collecting this evidence?

Option 5. You are investigating a hit-and-run accident and have identified a suspect vehicle. Describe how you would collect paint to determine whether the suspect vehicle was involved in the accident. Be sure to indicate the tools you would use and the steps you would take to prevent cross-contamination.

Option 6. While investigating a murder scene, police gather evidence that includes a dead body riddled with stab sounds, fingerprints on a bloody knife found near the body, and a ticket stub from a theater several miles away from the scene. Detectives determine that the knife belongs to the victim, but matched prints on the knife to an acquaintance of the victim. When questioned, the acquaintance claims he was at the movies at the time of the murder – the same movie shown on the ticket stub at the scene. What direct physical evidence connects the acquaintance to the crime scene? What circumstantial evidence connects him to the scene? What can you conclude about the acquaintance’s involvement solely from direct physical evidence and deductive reasoning? What might you conclude considering circumstantial evidence and inductive reasoning as well?

Option 7: Criminalist Mick is collecting evidence from a fire scene. He gathers about a quart of ash and soot debris from several rooms surrounding the point of origin. He stores the debris in a new, clean paint can, filled about three-quarters full. Seeing several pieces of timber he believes may contain accelerant residues, he cuts them and places them in airtight plastic bags. A short time later a suspect is arrested and Mick searches him for any signs of an igniter or accelerant. He finds a cigarette lighter on the suspect and seizes it for evidence before turning the suspect over to the police. What mistakes, if any, did Mick make in collecting the evidence?

Option 8: List and describe the four types of impact bloodstain spatter patterns.

Option 9: What are the characteristics of gunshot spatter and of cast-off spatter?

Option 10: Describe the procedures to document bloodstain pattern evidence.

Option 11: List and give the characteristics of seven of the major generic fibers not addressed by another student.

Option 12: The identification and comparison of manufactured fibers consists of at least three examinations and comparisons. List and describe them.

Option 13: Briefly describe the chemistry of fire.

Option 14: Define conduction, radiation, and convection.

Option 15: List the characteristics of a fire scene that would indicate the use of accelerants.

MAKE SURE TO SITE YOUR WORK !!!!!!!! HAS TO BE 150 OR MORE WORDS NOT INCLUDING THE REFERNCES

The Sam Sheppard Case: A Trail of Blood

Convicted in 1954 of bludgeoning his wife to death, Dr. Sam Sheppard achieved celebrity status when the storyline of TV’s The Fugitive was apparently modeled on his efforts to seek vindication for the crime he professed not to have committed. Dr. Sheppard, a physician, claimed he was dozing on his living room couch when his pregnant wife, Marilyn, was attacked. Sheppard’s story was that he quickly ran upstairs to stop the carnage, but was knocked unconscious briefly by the intruder. The suspicion that fell on Dr. Sheppard was fueled by the revelation that he was having an adulterous affair. At trial, the local coroner testified that a pool of blood on Marilyn’s pillow contained the impression of a “surgical instrument.” After Sheppard had been imprisoned for ten years, the U.S. Supreme Court set aside his conviction due to the “massive, pervasive, and prejudicial publicity” that had attended his trial.

In 1966, the second Sheppard trial commenced. This time, the same coroner was forced to back off from his insistence that the

bloody outline of a surgical instrument was present on Marilyn’s pillow. However, a medical technician from the coroner’s

office now testified that blood on Dr. Sheppard’s watch was from blood spatter, indicating that Dr. Sheppard was wearing the watch in the presence of the battering of his

wife. The defense countered with the expert testimony of eminent criminalist Dr. Paul Kirk. Dr. Kirk concluded that blood spatter marks in the bedroom showed the killer to be left-handed. Dr. Sheppard was right-handed.

Dr. Kirk further testified that Sheppard stained his watch while attempting to obtain a pulse reading. After less than 12 hours of deliberation, the jury failed to convict Sheppard. But the ordeal had taken its toll. Four years later Sheppard died, a victim of drug and alcohol abuse.

headline news

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After studying this chapter, you should be able to: • Define crime-scene reconstruction

• Discuss the information that can be gained from bloodstain pattern analysis about the events involved in a violent crime

• Explain how surface texture, directionality, and angle of impact affect the shape of individual bloodstains

• Calculate the angle of impact of a bloodstain using its dimensions

• Describe the classifications of low-, medium-, and high-velocity impact spatter and appreciate how these classifications should be used

• Discuss the methods to determine the area of convergence and area of origin for impact spatter patterns

• Understand how various blood pattern types are created and which features of each pattern can be used to aid in reconstructing events at a crime scene

• Describe the methods for documenting bloodstain patterns at a crime scene

crime–scene reconstruction: bloodstain pattern analysis angle of impact

area of convergence area of origin arterial spray back spatter cast-off crime-scene

reconstruction drip trail pattern expirated blood

pattern flows forward spatter high-velocity spatter impact spatter low-velocity spatter medium-velocity

spatter satellite spatter skeletonization transfer pattern void

KEY TERMS

> > > > > > > > > > > > chapter 12

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crime-scene reconstruction The method used to support a likely sequence of events at a crime scene by the observation and evaluation of physical evidence and statements made by individuals involved with the incident

298 CHAPTER 12

Fundamentals of Crime-Scene Reconstruction Previous discussions dealing with the processes of identification and comparison have stressed laboratory work routinely performed by forensic scientists. However, there is another dimension to the role that forensic scientists play during the course of a criminal investigation: participat- ing in a team effort to reconstruct events that occurred before, during, and after the commission of a crime.

Law enforcement personnel must take proper action to enhance all aspects of the crime- scene search so as to optimize the crime-scene reconstruction. First, and most important, is securing and protecting the crime scene. Protecting the scene is a continuous endeavor from the beginning to the end of the search. Evidence that can be invaluable to reconstructing the crime can be unknowingly altered or destroyed by people trampling through the scene, ren- dering the evidence useless. The issue of possible contamination of evidence will certainly be attacked during the litigation process and could make the difference between a guilty and not-guilty verdict.

Before processing the crime scene for physical evidence, the investigator should make a preliminary examination of the scene as it was left by the perpetrator. Each crime scene pres- ents its own set of circumstances. The investigator’s experience and the presence or absence of physical evidence become critical factors in reconstructing a crime. The investigator cap- tures the nature of the scene as a whole by performing an initial walk-through of the crime scene and contemplating the events that took place. Using the physical evidence available to the naked eye, he or she can hypothesize about what occurred, where it occurred, and when it occurred. During the walk-through, the investigator’s task is to document observations and formulate how the scene should ultimately be processed. As the collection of physical evi- dence begins, any and all observations should be recorded through photographs, sketches, and notes. By carefully collecting physical evidence and thoroughly documenting the crime scene, the investigator can begin to unravel the sequence of events that took place during the com- mission of the crime.

Often reconstruction requires the involvement of law enforcement personnel, a medical ex- aminer, and/or a criminalist. All of these professionals contribute unique perspectives to develop the crime-scene reconstruction. Was more than one person involved? How was the victim killed? Were actions taken to cover up what took place? The positioning of the victim in a crime scene can often reveal pertinent information for the investigation. Trained medical examiners can ex- amine the victim at a crime scene and determine whether the body has been moved after death by evaluating the livor distribution within the body (see pages 72–73). For example, if livor has developed in areas other than those closest to the ground, the medical examiner can reason that the victim was probably moved after death. Likewise, the examiner can determine whether the victim was clothed after death because livor will not develop in areas of the body that are re- stricted by clothing.

A criminalist or trained crime-scene investigator can also bring special skills to the recon- struction of events that occurred during the commission of a crime. For example, a criminalist us- ing a laser beam to plot the approximate bullet path in trajectory analysis can help determine the probable position of the shooter relative to that of the victim (see Figure 12–1). Other skills that a criminalist may employ during a crime-scene reconstruction analysis include determining the direction of impact of projectiles penetrating glass objects (see pages 107–108); locating gunshot residues deposited on the victim’s clothing for the purpose of estimating the distance of a shooter from a target (see pages 427–430); searching for primer residues deposited on the hands of a sus- pect shooter (see pages 431–434); and, as we will see from the discussion that follows, analyzing blood spatter patterns.

Crime-scene reconstruction is the method used to support a likely sequence of events at a crime scene by observing and evaluating physical evidence and statements made by individuals involved with the incident. The evidence may also include informa- tion obtained from reenactments. Therefore, reconstructions have the best chance of being accurate when investigators use proper documentation and collection methods for all types of evidence.

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satellite spatter Small droplets of blood that are distributed around the perimeter of a drop or drops of blood and were produced as a result of the blood impacting the target surface

CRIME-SCENE RECONSTRUCTION: BLOODSTAIN PATTERN ANALYSIS 299

Bullet entrance wound

Search path for evidence of shooter

Laser

Mannequin

Window

Bullet hole

FIGURE 12–1 A laser beam is used to determine the search area for the position of a shooter who has fired a bullet through a window and wounded a victim. The bullet path is determined by lining up the victim’s bullet wound with the bullet hole present in the glass pane.

General Features of Bloodstain Formation Crimes involving violent contact between individuals are frequently accompanied by bleeding and resultant bloodstain patterns. Crime-scene analysts have come to appreciate that bloodstain patterns deposited on floors, walls, ceilings, bedding, and other relevant objects can provide valu- able insights into events that occurred during the commission of a violent crime. The information one is likely to uncover as a result of bloodstain pattern interpretation includes the following:

• The direction from which blood originated • The angle at which a blood droplet struck a surface • The location or position of a victim at the time a bloody wound was inflicted • The movement of a bleeding individual at the crime scene • The minimum number of blows that struck a bleeding victim • The approximate location of an individual delivering blows that produced a bloodstain pattern

The crime-scene investigator must not overlook the fact that the location, distribution, and appearance of bloodstains and spatters may be useful for interpreting and reconstructing the events that accompanied the bleeding. A thorough analysis of the significance of the position and shape of blood patterns with respect to their origin and trajectory is exceedingly complex and re- quires the services of an examiner who is experienced in such determinations. Most important, the interpretation of bloodstain patterns necessitates a carefully planned control experiment us- ing surface materials comparable to those found at the crime scene. This chapter presents the ba- sic principles and common deductions behind bloodstain pattern analysis to give the reader general knowledge to use at the crime scene.

Surface Texture Surface texture is of importance in the interpretation of bloodstain patterns arising from blood dripping off an object. Comparisons between standards and unknowns are valid only when iden- tical surfaces are used. In general, harder and nonporous surfaces (such as glass or smooth tile) result in less spatter. Rough surfaces, such as carpeting or wood, usually result in irregularly shaped stains with serrated edges, possibly with satellite spatter (see Figure 12–2).

Direction and Angle of Impact An investigator may discern the direction of travel of blood striking an object by studying the stain’s shape. As the stain becomes more elliptical in shape, its direction of impact becomes more

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angle of impact The acute angle formed between the path of a blood drop and the surface that it contacts

300 CHAPTER 12

(b)(a)

FIGURE 12–2 (a) A bloodstain from a single drop of blood that struck a glass surface after falling 24 inches. (b) A bloodstain from a single drop of blood that struck a cotton muslin sheet after falling 24 inches. (a) Courtesy A. Y. Wonder; (b) courtesy, A. Y. Wonder

FIGURE 12–3 A bloodstain pattern produced by drops of blood that were traveling from left to right. Courtesy A. Y. Wonder

discernible because the pointed end of a bloodstain faces its direction of travel. Also, the distorted or disrupted edge of an elongated stain indicates the direction of travel of the blood. In Figure 12–3, the bloodstain pattern was produced by several drops of blood that were traveling from left to right before striking a flat, level surface.

It is possible to determine the impact angle of blood on a flat surface by measuring the degree of circular distortion of the stain. A drop deposited at an angle of impact of about 90 degrees (directly vertical to the surface) will be approximately circular in shape with no tail or buildup of

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back spatter Blood directed back toward the source of the force that caused the spatter

forward spatter Blood that travels away from the source in the same direction as the force that caused the spatter

impact spatter A bloodstain pattern produced when an object makes forceful contact with a source of blood, projecting drops of blood outward from the source

WEBEXTRA 12.1 See How Bloodstain Spatter Patterns Are Formed www.mycrimekit.com

CRIME-SCENE RECONSTRUCTION: BLOODSTAIN PATTERN ANALYSIS 301

blood. However, as the angle of impact deviates from 90 degrees, the stain becomes elongated in shape. Buildup of blood will show up in the larger angles, whereas longer and longer tails will appear as the angle of impact becomes smaller (see Figure 12–4).

Impact Bloodstain Spatter Patterns One of the most common type of bloodstain pattern found at a crime scene is impact spatter. This pattern occurs when an object impacts a source of blood. The spatter projected outward and away from the source, such as an exit wound, is called a forward spatter. Back spatter, some- times called blowback spatter, consists of the blood projected backward from a source, such as an entrance wound, potentially being deposited on the object or person creating the impact. Im- pact spatter patterns consist of many drops radiating in direct lines from the origin of blood to the target (see Figure 12–5).

Investigators have derived a common classification system of impact spatter from the velocity of a blood droplet. In general, as the force of the impact on the source of blood increases, so does the velocity of the blood drops emanating from the source. It is also generally true that as both the force and velocity of impact increase, the diameter of the resulting blood drops decreases.

Classifying Impact Spatter LOW-VELOCITY SPATTER An impact pattern consisting of large separate or compounded drops with diameters of 3 millimeters or more is known as low-velocity spatter. This kind of spatter is

FIGURE 12–4 The higher pattern is of a single drop of human blood that fell 24 inches and struck hard, smooth cardboard at 50 degrees. On this drop the irregular edge shows the direction. The lower pattern is of a single drop of human blood that fell 24 inches and struck hard, smooth cardboard at 15 degrees. On this drop the tail shows the direction. Courtesy A. Y. Wonder

low-velocity spatter An impact spatter pattern created by a force traveling at 5 feet per second or less and producing drops with diameters greater than 3 millimeters

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medium-velocity spatter An impact spatter pattern created by a force traveling at 5 to 25 feet per second and producing drops with diameters between 1 and 3 millimeters

302 CHAPTER 12

FIGURE 12–5 Impact spatter produced by an automatic weapon. The arrows shows the multiple directions of travel from origin of impact as several different bullet struck the target. Courtesy A. Y. Wonder

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The distorted or disrupted edge of an elongated stain indicates the direction of travel of the blood drop. One may establish the location or origin of bloodshed by determining the directionality of the stain and the angle at which blood came into con- tact with the landing surface. To determine the an- gle of impact, calculate the stain’s length-to-width ratio and apply the formula

width of blood stain Sin A = ————–——––——

length of blood stain

normally produced by minimal force. Typically, the drops hit the surface at a speed of less than 5 feet per second.

MEDIUM-VELOCITY SPATTER A pattern consisting of small drops with diameters from 1 to 3 millimeters is classified as medium-velocity spatter. This type of impact spatter is normally associated with blunt-force trauma to an individual. Drops of medium-velocity spatter hit the surface at 5 to 25 feet per second.

HIGH-VELOCITY SPATTER Very fine drops with diameters of less than 1 millimeter are classi- fied as high-velocity spatter. Here the drops hit the surface at 100 feet per second or faster. Gunshot exit wounds or explosions commonly produce this type of spatter. However, because the drops are very small, they may not travel far; they may fall to the floor or ground where investigative personnel could overlook them.

where A = the angle of impact. For example, suppose the width of a stain is

11 mm and the length is 22 mm.

11 mm Sin A = -–––––– = 0.5

22mm

A scientific calculator with trigonometric functions will calculate that a sine of 0.50 corresponds to a 30-degree angle.

Note: There is a 5-degree error factor with this formula. This means that calculations are good to plus or minus 5 degrees of the actual value of the angle of impact. The measurements for length and width should be made with a ruler, micrometer, or photographic loupe.

high-velocity spatter An impact spatter pattern created by a force traveling at 100 feet per second or faster and producing drops with diameters less than 1 millimeter

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CRIME-SCENE RECONSTRUCTION: BLOODSTAIN PATTERN ANALYSIS 303

(a)

FIGURE 12–6 (a) The action associated with producing impact spatter. (b) The action associated with producing cast-off spatter. (c) The action associated with producing arterial spray spatter. Courtesy of A. Y. Wonder

(b)

Using droplet size to classify impact patterns by velocity is a useful tool for giving investi- gators insight into the general nature of a crime. However, the velocity at which blood strikes a surface by itself cannot illuminate the specific events that produced the spatter pattern. For ex- ample, beatings can produce high-velocity spatter or patterns that look more like low-velocity spatter. In general, one should use velocity categories very cautiously and for descriptive pur- poses only in evaluating impact spatter patterns.

As we will learn, blood spatter patterns can arise from a number of distinctly different sources. Illustrations of patterns emanating from impact (just discussed), cast-off (on page 306), and arterial spray (on page 307) are shown in Figure 12–6.

(c)

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304 CHAPTER 12

Convergence

FIGURE 12–7 An illustration of stain convergence on a two- dimensional plane. Convergence represents the area from which the stains emanated. Courtesy Judith Bunker, J. L. Bunker & Assoc., Ocoee, Fla.

Origin-of-Impact Patterns Impact spatter patterns can offer investigators clues that help determine the origin of the blood source and the position of the victim at the time of the impact.

AREA OF CONVERGENCE The area of convergence is the area on a two-dimensional plane from which the drops originated. This can be established by drawing straight lines through the long axis of several individual bloodstains, following the line of their tails. The intersection of these lines is the area of convergence, and the approximate area of origin will be on a line straight out from this area. Figure 12–7 illustrates how to draw lines to find an area of convergence.

An object hitting a source of blood numerous times will never produce exactly the same pattern each time. One may therefore determine the number of impacts by drawing the area of convergence for groups of stains from separate impacts.

AREA OF ORIGIN It may also be important to determine the area of origin of a bloodstain pat- tern, the area in a three-dimensional space from which the blood was projected. This will show the position of the victim or suspect in space when the stain-producing event took place. The dis- tribution of the drops in an impact pattern gives a general idea of the distance from the blood source to the bloodstained surface. Impact patterns produced at a distance close to the surface will appear as clustered stains. As the distance from the surface increases, so do the distribution and distance between drops.

A common method for determining the area of origin at the crime scene is called the string method. Figure 12–8 illustrates the steps in the string method:

1. Find the area of convergence for the stain pattern. 2. Place a pole or stand as an axis coming from the area of convergence. 3. Attach one end of a string next to each droplet. Place a protractor next to each droplet and

lift the string until it lines up with the determined angle of impact of the drop. Keeping the string in line with the angle, attach the other end of the string to the axis pole.

4. View the area of origin of the drops where the strings appear to meet. Secure the strings at this area.

This method produces an approximation of the area of origin with an error of 2 feet.

area of convergence The area on a two-dimensional plane where lines traced through the long axis of several individual bloodstains meet; this approximates the two-dimensional place from which the bloodstains were projected

area of origin The location in three-dimensional space that blood that produced a bloodstain originated from; the location of the area of convergence and the angle of impact for each bloodstain is used to approximate this area

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CRIME-SCENE RECONSTRUCTION: BLOODSTAIN PATTERN ANALYSIS 305

FIGURE 12–8 An illustration of the string method used at a crime scene to determine the area of origin of blood spatter. Source: Bloodstain Pattern Evidence by Anita Y. Wonder, p. 47. Copyright Elsevier, 2007

More Bloodstain Spatter Patterns Gunshot Spatter A shooting may leave a distinct gunshot spatter pattern. This may be characterized by both for- ward spatter from an exit wound and back spatter from an entrance wound. However, the gunshot produces only back spatter if the bullet does not exit the body. If the victim is close enough to a

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306 CHAPTER 12

FIGURE 12–9 The high-velocity spatter from the cone-shaped deposit of gunshot spatter. Courtesy A. Y. Wonder

FIGURE 12–10 Back spatter bloodstains entering the muzzle of a weapon discharged in close proximity to a victim. Courtesy Ralph R. Ristenbatt III and Robert Shaler

vertical surface when suffering a gunshot wound, the blood will be expelled both forward and backward. This will leave a pattern of very fine drops radiating out in a cone-shaped pattern char- acteristic of high-velocity spatter (see Figure 12–9).

The location of the injury, the size of the wound created, and the distance between the victim and the muzzle of the weapon all affect the amount of back spatter that occurs. Finding high- velocity spatter containing the victim’s blood on a suspect can help investigators place the suspect in the vicinity when the gun was discharged. Back spatter created by a firearm discharge generally contains fewer and smaller atomized stains than does forward spatter. A muzzle blast striking an entrance wound will cause the formation of atomized blood.

Depending on the distance from the victim at which the gun was discharged, some back spatter may strike the gunman and enter the gun muzzle. This is called the drawback effect. Blood within the muzzle of a gun can place the weapon in the vicinity of the gunshot wound. The pres- ence of blowback spatter on a weapon’s muzzle is consistent with the weapon being close to the victim at the time of firing (see Figure 12–10).

Cast-Off Spatter A cast-off pattern is created when a blood-covered object flings blood in an arc onto a nearby surface. This kind of pattern commonly occurs when a person pulls a bloody fist or weapon back between delivering blows to a victim (see Figure 12–6[b]). The bloodstain tails will point in the direction that the object was moving.

The width of the cast-off pattern created by a bloody object may help suggest the kind of ob- ject that produced the pattern. The sizes of the drops are directly related to the size of the point from which they were propelled. Drops propelled from a small or pointed surface will be smaller and the pattern more linear; drops propelled from a large or blunt surface will be larger and the pattern wider. The volume of blood deposited on an object from the source also affects the size and number of drops in the cast-off pattern. The less blood on the object, the smaller the stains produced. The pat- tern may also suggest whether the blow that caused the pattern was directed from right to left or left to right. The pattern will point in the direction of the backward thrust, which will be opposite the di- rection of the blow. This could suggest which hand the assailant used to deliver the blows.

Cast-off patterns may also show the minimum number of blows delivered to a victim. Each blow should be marked by an upward-and-downward or forward-and-backward arc pattern

cast-off A bloodstain pattern that is created when blood is flung from a blood- bearing object in motion onto a surface

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CRIME-SCENE RECONSTRUCTION: BLOODSTAIN PATTERN ANALYSIS 307

(see Figure 12–11). By counting and pairing the patterns, one can estimate the minimum number of blows. An investigator should take into consideration that the first blow would only cause blood to pool to the area; it would not produce a cast-off pattern. Also, some blows may not come into contact with blood and so will not produce a pattern. The medical examiner is in the best position to estimate the number of blows a victim received.

Arterial Spray Spatter Arterial spray spatter is created when a victim suffers an injury to a main artery or the heart. The pressure of the continuing pumping of blood causes blood to spurt out of the injured area (see Figure 12–6[c]). Commonly, the pattern shows large spurted stains for each time the heart pumps. Some radial spikes, satellite spatter, or flow patterns may be evident because of the large volume of blood being expelled with each spurt. Drops may also be seen on the surface in fairly uniform size and shape and in parallel arrangement (see Figure 12–12).

The lineup of the stains shows the victim’s movement. Any vertical arcs or waves in the line show fluctuations in blood pressure. The larger arterial stains are at the end of the overall pattern. The initial breach can produce a mist effect from the initial pressure. Then, as the pressure drops, larger blood deposits occur because arterial pressure is not causing them to break up. Arterial pat- terns can also be differentiated because the oxygenated blood spurting from the artery tends to be a brighter red color than blood expelled from impact wounds.

Expirated Blood Patterns A pattern created by blood that is expelled from the mouth or nose from an internal injury is called an expirated blood pattern. If the blood that creates such a pattern is under great pressure, it produces very fine high-velocity spatter. Expirated blood at very low velocities produces a stain cluster with irregular edges (see Figure 12–13). The presence of bubbles of oxygen in the drying drops can differentiate a pattern created by expirated blood from other types of bloodstains. Expirated blood also may be lighter in color when compared to impact spatter as a result of dilu- tion by saliva. The presence of expirated blood gives an important clue as to the injuries suffered and the events that took place at a crime scene.

arterial spray A characteristic bloodstain pattern containing spurts that resulted from blood exiting under pressure from an arterial injury

FIGURE 12–11 The castoff pattern created from one backward and one forward motion of an overhand swing. The larger drops are away from the victim because they’re made when the weapon holds the greatest amount of blood. The smaller spatters are directed toward the victim. Source: Bloodstain Pattern Evidence by Anita Y. Wonder, p. 295. Copyright Elsevier, 2007

FIGURE 12–12 Arterial spray spatter found at a crime scene where a victim suffered injury to an artery. Courtesy Norman H. Reeves, Bloodstain Pattern Analysis, Tucson, Ariz., www.bloody1.com

expirated blood pattern A pattern created by blood that is expelled out of the nose, mouth, or respiratory system as a result of air pressure and/or airflow

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308 CHAPTER 12

FIGURE 12–13 An example of expirated blood expelled with two wheezes from the mouth. Courtesy A. Y. Wonder

void An area within a deposited spatter pattern that is clear of spatter, caused by an object or person blocking the area at the time of the spatter’s deposition

he was unable to save Dillon, who later died from his injuries. Police found that Dillon’s untied boot had been the cause of his shotgun wound. They determined that he had tripped while running with his loaded gun and shot himself. The grief-stricken Scher aroused no suspi- cion, so the shooting was ruled an accident.

Shortly thereafter, Scher moved from the area, di- vorced his wife, and married Dillon’s widow. This was too suspicious to be ignored; police reopened the case and decided to reconstruct the crime scene. The re- construction provided investigators with several pieces

forensics at work

Stephen Scher banged on the door of a cabin in the woods outside Montrose, Pennsylvania. According to Scher, his friend, Marty Dillon, had just shot himself while chasing after a porcupine. The two had been skeet shooting at Scher’s cabin, enjoying a friendly sporting weekend, when Dillon spotted a porcupine and took off out of sight. Scher heard a single shot and waited to hear his friend’s voice. After a few moments, he chased after Dillon and found him lying on the ground near a tree stump, bleeding from a wound in his chest. Scher administered CPR after locating his dying friend, but

Void Patterns A void is created when an object blocks the deposition of blood spatter onto a target surface or object (see Figure 12–14). The spatter is deposited onto the object or person instead. The blank space on the surface or object may give a clue as to the size and shape of the missing object or person. Once the object or person is found, the missing piece of the pattern should fit in, much like a puzzle piece, with the rest of the pattern. Voids may be applicable for establishing the body position of the victim or assailant at the time of the incident.

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FIGURE 12–14 A void pattern is found behind the door where the surface of the door blocked the deposition of spatter on that area. This void, and the presence of spatter on the door, shows that the door was open when the spatter was deposited. Courtesy Norman H. Reeves, Bloodstain Pattern Analysis, Tucson, Ariz., www.bloody1.com

transfer pattern A bloodstain pattern created when a surface that carries wet blood comes in contact with a second surface; recognizable imprints of all or a portion of the original surface or the direction of movement may be observed

of blood evidence that pointed to Scher as Dillon’s murderer.

Police noticed that Scher’s boots bore the unmis- takable spray of high-velocity impact blood spatter, ev- idence that he was standing within an arm’s length of Dillon when Dillon was shot. This pattern of bloodstains cannot be created while administering CPR, as Scher claimed had happened. The spatter pattern also clearly refuted Scher’s claim that he did not witness the inci- dent. In addition, the tree stump near Dillon’s body bore the same type of blood spatter, in a pattern that indi-

forensics at work

cated Dillon was seated on the stump and not running when he was shot. Finally, Dillon’s ears were free of the high-velocity blood spatter that covered his face, but blood was on his hearing protectors found nearby. This is a clear indication that he was wearing his hearing pro- tectors when he was shot and they were removed before investigators arrived. This and other evidence resulted in Scher’s conviction for the murder of his longtime friend, Marty Dillon.

Other Bloodstain Patterns Not all bloodstains at a crime scene appear as spatter patterns. The circumstances of the crime often create other types of stains that can be useful to investigators.

Contact/Transfer Patterns When an object with blood on it touches one that does not have blood on it, this produces a contact or transfer pattern. Examples of transfers with features include fingerprints (see Figure 12–15), handprints, footprints, footwear prints, tool prints, and fabric prints in blood. These may provide further leads by offering individual characteristics.

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310 CHAPTER 12

The size and general shape of a tool may be seen in a simple transfer. This can lead to narrowing the possible tools by class characteristics. A transfer that shows a very individualistic feature may help point to the tool that made the pattern.

Simple transfer patterns are produced when the object makes contact with the surface and the object is removed without any movement. Other transfers known as swipe patterns may be caused by movement of the bloody object across a surface. Generally, the swipe pattern will lighten and “feather” as the pattern moves away from the initial contact point (see Figure 12–16). The direc- tion of separate bloody transfers, such as footwear prints in blood, may show the movement of the suspect, victim, or others through the crime scene after the blood was present. The first trans- fer pattern will be dark and heavy with blood, whereas subsequent transfers will be increasingly lighter in color. As the transfers get lighter, less and less of the transferring object’s surface will deposit visible traces of blood. Bloody shoe imprints may also suggest whether the wearer was running or walking. Running typically produces imprints with more space between them and more satellite or drop patterns between each imprint.

Flows Patterns made by drops or large amounts of blood flowing by the pull of gravity are called flows. Flows may be formed by single drops or large volumes of blood coming from an actively bleeding wound or blood deposited on a surface such as from an arterial spurt. Clotting of the blood’s solid parts may occur when a flow extends onto an absorbent surface.

The flow direction may show movements of objects or bodies while the flow was still in progress or after the blood had dried. Figure 12–17 illustrates a situation in which movement of the surface while the flow was still in progress led to a specific pattern.

FIGURE 12–15 A transfer pattern consisting of bloody fingerprints with apparent ridge detail. Courtesy Lawrence A. Presley, Arcadia University

FIGURE 12–16 A series of swipe patterns moving from right to left. Courtesy A. Y. Wonder

flow pattern A bloodstain pattern formed by the movement of small or large amounts of blood as a result of gravity’s pull

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CRIME-SCENE RECONSTRUCTION: BLOODSTAIN PATTERN ANALYSIS 311

FIGURE 12–17 The flow pattern suggests that the victim was upright and then fell while blood flowed. The assailant claimed the victim was stabbed while sleeping. Source: Bloodstain Pattern Evidence by Anita Y. Wonder, p. 98. Copyright Elsevier, 2007

Interruption of a flow pattern may be helpful in assessing the sequence and passage of time between the flow and its interruption. If a flow found on an object or body does not appear con- sistent with the direction of gravity, one may surmise that the object or body was moved after the blood had dried.

Pools A pool of blood occurs when blood collects in a level (not sloped) and undisturbed place. Blood that pools on an absorbent surface may be absorbed throughout the surface and diffuse, creating a pattern larger than the original pool. This often occurs to pools on beds or sofas.

The approximate drying time of a pool of blood is related to the environmental condition of the scene. By experimentation, an analyst may be able to reasonably estimate the drying times of stains of different sizes. Small and large pools of blood can aid in reconstruction by providing an estima- tion of the amount of time that elapsed since the blood was deposited. Considering the drying time of a blood pool can yield information about the timing of events that accompanied the incident.

The edges of a stain will dry to the surface, producing a phenomenon called skeletonization (see Figure 12–18). This usually occurs within 50 seconds of deposition of drops, and longer for larger volumes of blood. If the central area of the pooled bloodstain is altered by wiping, the skele- tonized perimeter will be left intact. This can be used to interpret whether movement or activity occurred shortly after the pool was deposited, or whether the perimeter had time to skeletonize be- fore the movement occurred. This may be important for classifying the source of the original stain.

Drip Trail Patterns A drip trail pattern is a series of drops that are separate from other patterns, formed by blood dripping off an object or injury. The stains form a kind of line or path usually made by the sus- pect after injuring or killing the victim, or they can show the movement of a wounded victim. It may simply show movement, lead to a discarded weapon, or provide identification of the suspect by his or her own blood. Investigators often see this type of pattern in stabbings during which the suspect cuts himself or herself as a result of the force necessary to stab the victim. Figure 12–19 shows a drip trail pattern away from the center of action at a crime scene.

skeletonization The process by which the edges of a stain dry to the surface in a specific period of time (dependent on environmental and surface conditions); skeletonization remains apparent even after the rest of the bloodstain has been disturbed from its original position

drip trail pattern A pattern of bloodstains formed by the dripping of blood off a moving surface or person in a recognizable pathway separate from other patternsIS

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312

FIGURE 12–18 Skeletonization is shown in a bloodstain that was disturbed after the edges had time to skeletonize. Courtesy Norman H. Reeves, Bloodstain Pattern Analysis, Tucson, Ariz., www.bloody1.com

FIGURE 12–19 A drip trail pattern leads away from the center of the mixed bloodstain pattern. Courtesy Norman H. Reeves, Bloodstain Pattern Analysis, Tucson, Ariz., www.bloody1.com

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String grid – Two-foot squares

= Lettered or numbered label in each square

FIGURE 12–20 The grid method may be used for photographing bloodstain pattern evidence. Source: R. R. Ogle, Jr., Crime Scene Investigation and Reconstruction, 2nd ed., Prentice Hall, Upper Saddle River, N.J., 2007

Measurement rulers

Small metric rulers

Areas with bloodstain patterns

FIGURE 12–21 The perimeter ruler method may be used for photographing bloodstain pattern evidence. Source: R. R. Ogle, Jr., Crime Scene Investigation & Reconstruction, 2nd ed., Prentice Hall, Upper Saddle River, N.J., 2007

The shape of the stains in a drip trail pattern can help investigators determine the direction and speed at which a person was moving. The tails of the drops in a trail pattern point in the di- rection the person was moving. More circular stains are found where the person was moving slowly enough to not form tails. This information may be helpful in reconstruction.

Documenting Bloodstain Pattern Evidence Blood spatter patterns of any kind can provide a great deal of information about the events that took place at a crime scene. For this reason, investigators should note, study, and photograph each pattern and drop. This must be done to accurately record the location of specific patterns and to distinguish the stains from which laboratory samples were taken. The photographs and sketches can also point out specific stains used in determining the direction of force, angle of impact, and area of origin.

Just as in general crime-scene photography, the investigator should create photographs and sketches of the overall pattern to show the orientation of the pattern to the scene. The medium- range documentation should include pictures and sketches of the whole pattern and the relation- ships among individual stains within the pattern. The close-up photographs and sketches should show the dimensions of each individual stain. Close-up photographs should be taken with a scale of some kind apparent in the photograph.

Two common methods of documenting bloodstain patterns place attention on the scale of the patterns. The grid method involves setting up a grid of squares of known dimensions over the en- tire pattern using string and stakes (see Figure 12–20). All overall, medium-range, and close-up photographs are taken with and without the grid. The second method, called the perimeter ruler method, involves setting up a rectangular border of rulers around the pattern and then placing a small ruler next to each stain. In this method, the large rulers show scale in the overall and medium-range photos, whereas the small rulers show scale in the close-up photographs (see Figure 12–21). Some investigation teams use tags in close-up photographs to show evidence num- bers or other details.

An area-of-origin determination should be calculated whenever possible. All measurements of stains and calculations of angle of impact and point of origin should be recorded in crime-scene notes. Especially important stains can be roughly sketched within the notes.

Only some jurisdictions have a specialist on staff to decipher patterns either at the scene or from photographs at the lab. Therefore, it is important that all personnel be familiar with patterns to properly record and document them for use in reconstruction.

Virtual Forensics Lab

Blood Spatter Evidence To perform a virtual lab analysis of blood spatter evidence, go to www.pearsoncustom.com/us/vlm/

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from the perpetrator’s fist while inflicting blows. Arrow 2 in Figure 2 points to three transfer impression patterns di- rected left to right as the perpetrator’s bloodstained hand contacted the wall and as the fist blows were being inflicted on the victim. Arrow 3 in Figure 2 points to blood flow from the victim’s wounds as he slumped against the wall.

Figure 3 contains a series of laboratory test patterns created to evaluate the patterns contained within Figure 2.

Figure 4 shows how the origin of individual impact spatter patterns located on the wall and door and ema- nating from the bleeding victim can be documented by the determination of separate areas of convergence.

forensics at work

FIGURE 1 A three-dimensional diagram illustrating bloodstain patterns that were located, documented, and reconstructed. The Institute of Applied Forensic Technology, Ocoee, Florida

FIGURE 2 Positions of bloodstain patterns arising from blows that were inflicted on the victim’s face. The Institute of Applied Forensic Technology, Ocoee, Florida

314 CHAPTER 12

An elderly male was found lying dead on his living room floor. He had been beaten about the face and head, then stabbed in the chest and robbed. The reconstruc- tion of bloodstains found on the interior front door and the adjacent wall documented that the victim was beaten about the face with a fist and struck on the back of the head with his cane. A three-dimensional diagram illustrating the evidential bloodstain patterns is shown in figure 1.

A detail photograph of bloodstains next to the interior door is shown in Figure 2. Arrow 1 in Figure 2 points to the cast-off pattern directed left to right as blood was flung

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A suspect was apprehended three days later, and he was found to have an acute fracture of the right hand. When he was confronted with the bloodstain evidence, the suspect admitted striking the victim,

(a)

FIGURE 3 (a) A laboratory test pattern showing an impact spatter. The size and shape of the stains demonstrate a forceful impact 90 degrees to the target. (b) A laboratory test pattern illustrating a cast- off pattern directed left to right from an overhead swing. (c) A laboratory test pattern showing a repetitive transfer impression pattern produced by a bloodstained hand moving left to right across the target. (d) A laboratory test pattern illustrating vertical flow patterns. The left pattern represents a stationary source; the right pattern was produced by left-to- right motion. The Institute of Applied Forensic Technology, Ocoee, Florida

(b)

FIGURE 4 (a) A convergence of impact spatter patterns associated with beating with a fist. (b) The convergence of impact spatter associated with the victim falling to the floor while bleeding from the nose. (c) The convergence of impact spatter associated with the victim while face down at the door, being struck with a cane. The Institute of Applied Forensic Technology, Ocoee, Florida

forensics at work

first with his fist, then with a cane, and finally stabbing him with a kitchen knife. The suspect pleaded guilty to three first-degree felonies.

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316 CHAPTER 12

> > > > > > > > > > >chapter summary Physical evidence left behind at a crime scene, properly han- dled and preserved, plays a crucial role in reconstructing the events that took place surrounding the crime. Crime-scene re- construction relies on the combined efforts of medical exam- iners, criminalists, and law enforcement personnel to recover physical evidence and to sort out the events surrounding the occurrence of a crime.

The location, distribution, and appearance of bloodstains and spatters may be useful for interpreting and reconstructing the events that produced the bleeding. An investigator or blood- stain pattern analyst can decipher from individual bloodstains the directionality and angle of impact of the blood when it im- pacted the surface of deposition. In addition, bloodstain pat- terns, consisting of many individual bloodstains, may convey to the analyst the location of victims or suspects, the movement of bleeding individuals, and the number of blows delivered.

Surface texture and an individual stain’s shape, size, and location must be considered when determining the direction and angle of impact of the bloodstain. Surface texture can greatly affect the shape of a bloodstain. The directionality of an individual bloodstain may be shown by the stain’s tail or the accumulation of blood because the tail or accumulation ap- pears on the side opposite the force. The angle of impact of a bloodstain can be approximated by the shape of the blood- stain, or it can be more effectively estimated using the width- to-length ratio of the stain.

An impact spatter pattern occurs when an object impacts a source of blood producing forward spatter projected forward from the source and back spatter projected backward from the source. Patterns created by impact spatter can be classified as low-velocity (>3 mm drops), medium-velocity (1–3 mm drops), or high-velocity (<1 mm drops). These classifications are for descriptive purposes only and should not be used to determine the kind of force that produced the pattern. The area of conver- gence of an impact spatter pattern is the area the individual stains emanated from on a two-dimensional plane. The area of origin of a bloodstain pattern in three-dimensional space may

represent the position of the victim or suspect when the stain- producing event took place.

Gunshot spatter consists of very fine spatter originating from both forward spatter from an exit wound and back spat- ter from an entrance wound, or only back spatter if the bullet did not exit the body. Blood cast off from an object, typically a weapon or fist between delivering blows to a victim, may form an arc pattern on a nearby surface. The features of the pattern can suggest the kind of object that created it and the minimum number of blows delivered by the object. The char- acteristic spurts present in an arterial spray spatter are created by the continuing pumping of blood from an arterial injury. Expirated blood expelled from the mouth or nose may at first appear to be fine high-velocity or large low-velocity impact spatter. It may feature bubbles of oxygen in the drying drops or possibly be mixed with saliva. A void, where an object (or person) blocks the deposition of blood spatter onto a target surface or object, may give a clue as to the size and shape of the missing object or person.

Transfer patterns, created when an object with blood on it makes simple contact with a surface, may reveal the shape or texture characteristics of the object. Because the direction of flows originating from either a single drop or a large amount of blood is caused by gravity, the direction of a pattern may suggest the original position of the surface when the flow was formed. A drip trail pattern shows a path of drops separate from other patterns; it is formed by single blood drops drip- ping off an object or injury. The presence of skeletonization of the perimeter of a bloodstain suggests that the stain was dis- turbed after the edges had had sufficient time to skeletonize.

The precise appearance and location of each bloodstain at a crime scene is important. Therefore, each bloodstain pattern located at a crime scene must be properly documented in notes, photographs, and sketches. Medium-range and close-up photographs should be recorded using either the grid method or perimeter ruler method to show the orientation and relative size of the pattern and individual stains.

review questions

1. ___________ is the method used to support a likely se- quence of events at a crime scene by the observation and evaluation of physical evidence and statements made by individuals involved with the incident.

2. Reconstructing the circumstances of a crime scene is a team effort that may include the help of law enforcement personnel, medical examiners, and ___________.

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3. Violent contact between individuals at a crime scene frequently produces bleeding and results in the forma- tion of ___________.

4. The proper interpretation of bloodstain patterns necessi- tates carefully planned ___________ using surface ma- terials comparable to those found at the crime scene.

5. Bloodstain patterns may convey to the analyst the loca- tion and movements of ___________ or ___________ during the commission of a crime.

6. True or False: Harder and less porous surfaces result in less spatter, whereas rough surfaces result in stains with more spatter and serrated edges. ___________

7. Generally, bloodstain diameter (increases, decreases) with height. ___________

8. The ___________ and ___________ of blood striking an object may be discerned by the stain’s shape.

9. A drop of blood that strikes a surface at an angle of im- pact of approximately 90 degrees will be close to (ellip- tical, circular) in shape. ___________

10. The angle of impact of an individual bloodstain can be estimated using the ratio of ___________ divided by ___________.

11. ___________ is the most common type of blood spatter found at a crime scene and is produced when an object forcefully contacts a source of blood.

12. True or False: Forward spatter consists of the blood projected backward from the source, and back spatter is projected outward and away from the source. ___________

13. The classification system of impact spatter is based on the size of drops resulting from the velocity of the blood drops produced, and patterns can be classified as ___________, ___________, or ___________ impact spatter.

14. True or False: The velocity classification system is a good way to classify impact patterns and to determine the kind of force that produced them. ___________

15. The ___________ is the point on a two-dimensional plane from which the drops originated.

16. The ___________ of a bloodstain pattern in a three- dimensional space illustrates the position of the victim or suspect when the stain-producing event took place.

17. The ___________ method is used at the crime scene to determine the area of origin.

18. A(n) ___________ is created by contact between a bloody object and a surface.

19. Movement of a bloody object across a surface, (lightens, darkens) as the pattern moves away from the point of contact.

20. True or False: Footwear transfer patterns created by an individual who was running typically show imprints with more space between them compared to those of an individual who was walking. ___________

21. True or False: The direction of a flow pattern may show movements of objects or bodies while the flow was still in progress or after the blood had dried. ___________

22. The approximate drying time of a(n) ___________ of blood determined by experimentation is related to the environmental condition of the scene and may suggest how much time has elapsed since its deposition.

23. The edges of a bloodstain generally ___________ within 50 seconds of deposition and are left intact even if the central area of a bloodstain is altered by a wiping motion.

24. A(n) ___________ pattern commonly originates from repeated strikes from weapons or fists and is character- ized by an arc pattern of separate drops showing directionality.

25. True or False: Characteristics of a cast-off pattern arc cannot give clues as to the kind of object that was used to produce the pattern. ___________

26. When an injury is suffered to an artery, the pressure of the continuing pumping of blood projects blood out of the injured area in spurts creating a pattern known as ___________.

27. If a(n) ___________ pattern is found at a scene, it may show movement, lead to a discarded weapon, or provide identification of the suspect by his or her own blood.

28. A bloodstain pattern created by ___________ features bubbles of oxygen in the drying drops and may be lighter in color when compared to impact spatter.

29. The shape and size of the blank space, or ___________, created when an object blocks the deposition of spatter onto a surface and is then removed may give a clue as to the size and shape of the missing object or person.

30. True or False: Each bloodstain pattern found at a crime scene should be noted, studied, and photographed. ___________

31. When documenting bloodstain patterns, the ___________ involves setting up a grid of squares of known dimensions over the entire pattern and taking overview, medium-range, and close-up photographs with and without the grid.

32. The ___________ method of bloodstain documentation involves setting up a border of rulers around the pattern and then placing a small ruler next to each stain to show relative position and size in photographs.

33. True or False: The pointed end of a bloodstain always faces toward its direction of travel. ___________

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318 CHAPTER 12

application and critical thinking

1. After looking at the bloodstains in the figure, answer the following questions:

a. Which three drops struck the surface closest to a 90-degree angle? Explain your answer.

b. Which three drops struck the surface farthest from a 90-degree angle? Explain your answer.

c. In what direction were drops 2 and 7 traveling when they struck the surface? Explain your answer.

2. Investigator Priscilla Wright arrives at a murder scene and finds the body of a victim who suffered a gunshot wound, but she sees no blood spatter on the wall or floor behind it. What should she conclude from this observation?

3. Investigator Terry Martin arrives at an assault scene and finds a cast-off pattern consisting of tiny drops of blood in a very narrow linear arc pattern on a wall near the victim. What does this tell him about the weapon used in the crime?

1. 2. 3. 4.

5. 6.

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further references

Bevel, Tom, and Ross Gardner, Bloodstain Pattern Analysis: With an Introduction to Crime Scene Reconstruction, 3rd ed. Boca Raton, Fla.: CRC Press, 2008.

James, Stuart H., Paul E. Kish, and T. P. Sutton, Principles of Bloodstain Pattern Analysis: Theory and Practice. Boca Raton, Fla.: CRC Press, 2005.

Wonder, A. Y., Blood Dynamics. Burlington, Mass.: Else- vier Academic Press, 2001.

Wonder, A. Y., Bloodstain Pattern Evidence: Objective Approaches and Case Applications. Burlington, Mass.: Elsevier Academic Press, 2007.

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Jeffrey MacDonald: Fatal Vision

The grisly murder scene that confronted police on February 17, 1970, is one that cannot be wiped from memory. Summoned to the Fort Bragg residence of Captain Jeffrey MacDonald, a physician, police found the bludgeoned body of MacDonald’s wife. She had been repeatedly knifed, and her face was smashed to a pulp. MacDonald’s two children, ages 2 and 5, had been brutally and repeatedly knifed and battered to death. Suspicion quickly fell on MacDonald. To the eyes of investigators, the murder scene had a staged appearance. MacDonald described a frantic effort to subdue four intruders who had slashed at him with an ice pick. However, the confrontation left MacDonald with minor wounds and no apparent defense wounds on his arms. MacDonald then described how he had covered his slashed wife with his blue pajama top. Interestingly, when the body was removed blue threads were observed under the body. In fact, blue threads matching the pajama top turned up throughout the house—nineteen in one child’s bedroom,

including one beneath her fingernail, and two in the other child’s bedroom. Eighty-one blue fibers were recovered from

the master bedroom, and two were located on a bloodstained piece of wood outside the house. Later forensic examination showed that the 48 ice pick holes in the

pajama top were smooth and cylindrical, a sign that the top was stationary when it was slashed. Also, folding the pajama top demonstrated that the 48 holes actually could have been made by 21 thrusts of an ice pick. This coincided with the number of wounds that MacDonald’s wife sustained. As described in the book Fatal Vision, which chronicled the murder investigation, when MacDonald was confronted with adulterous conduct, he replied, “You guys are more thorough than I thought.” MacDonald is currently serving three consecutive life sentences.

headline news

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After studying this chapter you should be able to: • Recognize and understand the cuticle, cortex, and medulla

areas of hair

• List the three phases of hair growth

• Appreciate the distinction between animal and human hairs

• List hair features that are useful for the microscopic comparison of human hairs

• Explain the proper collection of forensic hair evidence

• Describe and understand the role of DNA typing in hair comparisons

• Understand the differences between natural and manufactured fibers

• List the properties of fibers that are most useful for forensic comparisons

• Describe the proper collection of fiber evidence

• List the most useful examinations for performing a forensic comparison of paint

• Describe the proper collection and preservation of forensic paint evidence

hairs, fibers, and paint

anagen phase catagen phase cortex cuticle follicular tag macromolecule manufactured fibers medulla mitochondrial DNA molecule monomer natural fibers nuclear DNA polymer telogen phase

KEY TERMS

> > > > > > > > > > > > chapter 13

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medulla A cellular column running through the center of the hair

cortex The main body of the hair shaft

cuticle The scale structure covering the exterior of the hair

322 CHAPTER 13

The trace evidence transferred between individuals and objects during the commission of a crime, if recovered, often corroborates other evidence developed during the course of an investigation. Although in most cases physical evidence cannot by itself positively identify a suspect, labora- tory examination may narrow the origin of such evidence to a group that includes the suspect. Using many of the instruments and techniques described in the previous three chapters, the crime laboratory has developed a variety of procedures for comparing and tracing the origins of physi- cal evidence. This chapter and those that follow discuss how to apply these techniques to the analysis of the types of physical evidence most often encountered at crime scenes. We begin with a discussion of hairs, fibers, and paint.

Morphology of Hair Hair is encountered as physical evidence in a wide variety of crimes. However, any review of the forensic aspects of hair examination must start with the observation that it is not yet possible to individualize a human hair to any single head or body through its morphology. Over the years, criminalists have tried to isolate the physical and chemical properties of hair that could serve as individual characteristics of identity. Partial success has finally been achieved by isolating and characterizing the DNA present in hair. The importance of hair as physical evidence cannot be underemphasized. Its removal from the body often denotes physical contact between a victim and perpetrator and hence a crime of a serious or violent nature. When hair is properly collected at the crime scene and submitted to the laboratory along with enough standard/reference samples, it can provide strong corroborative evidence for placing an individual at a crime site.

The first step in the forensic examination of hair logically starts with its color and structure, or morphology, and, if warranted, progresses to the more detailed DNA extraction, isolation, and characterization.

Hair is an appendage of the skin that grows out of an organ known as the hair follicle. The length of a hair extends from its root or bulb embedded in the follicle, continues into the shaft, and terminates at the tip end. The shaft, which is composed of three layers—the cuticle, cortex, and medulla—is subjected to the most intense examination by the forensic scientist (see Figure 13–1).

Cuticle Two features that make hair a good subject for establishing individual identity are its resistance to chemical decomposition and its ability to retain structural features over a long period of time. Much of this resistance and stability is attributed to the cuticle, the outside covering of the hair.

Cortex Cuticle

Follicle Root

FIGURE 13–1 Cross section of skin showing hair growing out of a tubelike structure called the follicle.

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HAIRS, FIBERS, AND PAINT 323

(a)

FIGURE 13–2 Scale patterns of various types of hair. (a) Human head hair (600�), (b) dog (1250�), (c) deer (120�), (d) rabbit (300�), (e) cat (2000�), and (f) horse (450�).

(b)

The cuticle is formed by overlapping scales that always point toward the tip end of each hair. The scales form from specialized cells that have hardened (keratinized) and flattened in pro- gressing from the follicle. The scales of most animal hair can best be described as looking like shingles on a roof. Although the scale pattern is not a useful characteristic for individualizing human hair, the variety of patterns formed by animal hair makes it an important feature for species identification. Figure 13–2 shows the scale patterns of some animal hairs and of a hu- man hair as viewed by the scanning electron microscope. Another method of studying the scale pattern of hair is to make a cast of its surface. This is done by embedding the hair in a soft medium, such as clear nail polish or softened vinyl. When the medium has hardened, the hair is removed, leaving a clear, distinct impression of the hair’s cuticle, ideal for examination with a compound microscope.

Cortex Contained within the protective layer of the cuticle is the cortex. The cortex is made up of spindle- shaped cortical cells aligned in a regular array, parallel to the length of the hair. The cortex derives its major forensic importance from the fact that it is embedded with the pigment granules that give hair its color. The color, shape, and distribution of these granules provide important points of comparison among the hairs of different individuals.

The structural features of the cortex are examined microscopically after the hair has been mounted in a liquid medium with a refractive index close to that of the hair. Under these condi- tions, the amount of light reflected off the hair’s surface is minimized, and the amount of light penetrating the hair is optimized.

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anagen phase The initial growth phase during which the hair follicle actively produces hair

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Medulla The medulla is a collection of cells that looks like a central canal running through a hair. In many animals, this canal is a predominant feature, occupying more than half of the hair’s diameter. The medullary index measures the diameter of the medulla relative to the diameter of the hair shaft and is normally expressed as a fraction. For humans, the index is generally less than one-third; for most other animals, the index is one-half or greater.

The presence and appearance of the medulla vary from individual to individual and even among the hairs of a given individual. Not all hairs have medullae, and when they do exist, the degree of medullation can vary. In this respect, medullae may be classified as being continuous, interrupted, fragmented, or absent (see Figure 13–3). Human head hairs generally exhibit no medullae or have fragmented ones; they rarely show continuous medullation. One noted excep- tion is the Mongoloid race, whose members usually have head hairs with continuous medullae. Also, most animals have medullae that are either continuous or interrupted.

Another interesting feature of the medulla is its shape. Humans, as well as many animals, have medullae that give a nearly cylindrical appearance. Other animals exhibit medullae that have a patterned shape. For example, the medulla of a cat can best be described as resembling a string of pearls, whereas members of the deer family show a medullary structure consisting of spheri- cal cells occupying the entire hair shaft. Figure 13–4 illustrates medullary sizes and forms for a number of common animal hairs and a human head hair.

A searchable database on CD-ROM of the 35 most common animal hairs encountered in forensic casework is commercially available.1 This database allows an examiner to rapidly search for animal hairs based on scale patterns and/or medulla type using a PC. A typical screen presen- tation arising from such a data search is shown in Figure 13–5.

Root The root and other surrounding cells within the hair follicle provide the tools necessary to pro- duce hair and continue its growth. Human head hair grows in three developmental stages, and the shape and size of the hair root is determined by the growth phase in which the hair happens to be. The three phases of hair growth are the anagen, catagen, and telogen phases.

In the anagen phase, which may last up to six years, the root is attached to the follicle for con- tinued growth, giving the root bulb a flame-shaped appearance (Figure 13–6[a]). When pulled from the root, some hairs in the anagen phase have a follicular tag. With the advent of DNA analysis, this follicular tag is important for individualizing hair.

Hair continues to grow, but at a decreasing rate, during the catagen phase, which can last anywhere from two to three weeks. In the catagen phase, roots typically take on an elongated appearance (Figure 13–6[b]) as the root bulb shrinks and is pushed out of the hair follicle.

Once hair growth ends, the telogen phase begins and the root takes on a club-shaped appearance (Figure 13–6[c]). Over two to six months, the hair is pushed out of the follicle, causing the hair to be naturally shed.

Identification and Comparison of Hair Most often the prime purpose for examining hair evidence in a crime laboratory is to establish whether the hair is human or animal in origin or to determine whether human hair retrieved at a crime scene compares with hair from a particular individual. Although animal hair can normally be distinguished from human hair with little difficulty, human hair comparisons must be undertaken

Continuous Interrupted Fragmented

FIGURE 13–3 Medulla patterns.

1 J. D. Baker and D. L. Exline, Forensic Animal Hair Atlas: A Searchable Database on CD-ROM. RJ Lee Group, Inc., 350 Hochberg Rd., Monroeville, Pa. 15146.

catagen phase A transition stage between the anagen and telogen phases of hair growth

telogen phase The final growth phase in which hair naturally falls out of the skin

follicular tag A translucent piece of tissue surrounding the hair’s shaft near the root; it contains the richest source of DNA associated with hair

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FIGURE 13–4 Medulla patterns for various types of hair. (a) Human head hair (400�), (b) dog (400�), (c) deer (500�), (d) rabbit (450�), (e) cat (400�), and (f) mouse (500�).

with extreme caution and with an awareness of hair’s tendency to exhibit variable morphological characteristics, not only from one person to another but also within a single individual.

Considerations in Hair Examination A careful microscopic examination of hair reveals morphological features that can distinguish human hair from animal hair. The hair of various animals also differs enough in structure that the examiner can often identify the species. Before reaching such a conclusion, however, the exam- iner must have access to a comprehensive collection of reference standards and the accumulated

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FIGURE 13–5 Information on rabbit hair contained within the Forensic Animal Hair Atlas. Courtesy RJ Lee Group, Inc. Monroeville, Pa.

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FIGURE 13–6 Hair roots in the (a) anagen phase, (b) catagen phase, and (c) telogen phase (100�). Courtesy Charles A. Linch

experience of hundreds of prior hair examinations. Scale structure, medullary index, and medullary shape are particularly important in hair identification.

The most common request when hair is used as forensic evidence is to determine whether hair recovered at the crime scene compares to hair removed from a suspect. In most cases, such a comparison relates to hair obtained from the scalp or pubic area. Ultimately, the evidential value of the comparison depends on the degree of probability with which the examiner can associate the hair in question with a particular individual.

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HAIR CHARACTERISTICS In making a hair comparison, a comparison microscope is an invalu- able tool that allows the examiner to view the questioned and known hair together, side by side. Any variations in the microscopic characteristics will thus be readily observed. Because hair from any part of the body exhibits a range of characteristics, it is necessary to have an adequate number of known hairs that are representative of all of its features when making a comparison.

In comparing hair, the criminalist is particularly interested in matching the color, length, and diameter. Other important features are the presence or absence of a medulla and the distribution, shape, and color intensity of the pigment granules in the cortex. A microscopic examination may also distinguish dyed or bleached hair from natural hair. A dyed color is often present in the cuti- cle as well as throughout the cortex. Bleaching, on the other hand, tends to remove pigment from the hair and to give it a yellowish tint. If hair has grown since it was last bleached or dyed, the natural-end portion will be quite distinct in color. An estimate of the time since dyeing or bleach- ing can be made because hair grows approximately one centimeter per month. Other significant but less frequent features may be observed in hair. For example, morphological abnormalities may be present because of certain diseases or deficiencies. Also, the presence of fungal and nit infections can further link a hair specimen to a particular individual.

POTENTIAL FOR ERROR Although microscopic comparison of hairs has long been accepted as an appropriate approach for including and excluding questioned hairs against standard/reference hairs, many forensic scientists have long recognized that this approach is subjective and is highly dependent on the skills and integrity of the analyst as well as the hair morphology being exam- ined. However, until the advent of DNA analysis, the forensic science community had no choice but to rely on the microscope to carry out hair comparisons.

Any lingering doubts about the necessity of augmenting microscopic hair examinations with DNA analysis evaporated with the publication of an FBI study describing significant error rates associated with microscopic comparison of hairs.2 Hair evidence submitted to the FBI for DNA analysis between 1996 and 2000 was examined both microscopically and by DNA analysis. Approximately 11 percent of the hairs (9 out of 80) in which FBI hair examiners found a positive microscopic match between questioned and standard/reference hairs were found to be non- matches when they were later subjected to DNA analysis. The course of events is clear; micro- scopic hair comparisons must be regarded by police and courts as presumptive in nature, and all positive microscopic hair comparisons must be confirmed by DNA determinations.

Questions Concerning Hair Examination A number of questions may be asked to further ascertain the present status of forensic hair examinations.

CAN THE BODY AREA FROM WHICH A HAIR ORIGINATED BE DETERMINED? Normally, it is easy to determine the body area from which a hair came. For example, scalp hairs generally show little diameter variation and have a more uniform distribution of pigment color when compared to other body hairs. Pubic hairs are short and curly, with wide variations in shaft diameter, and usually have continuous medullae. Beard hairs are coarse, are normally triangular in cross section, and have blunt tips acquired from cutting or shaving.

CAN THE RACIAL ORIGIN OF HAIR BE DETERMINED? In many instances, the examiner can distinguish hair originating from members of different races; this is especially true of Caucasian and Negroid head hair. Negroid hairs are normally kinky, containing dense, unevenly distributed pigments. Caucasian hairs are usually straight or wavy, with very fine to coarse pigments that are more evenly distributed when compared to Negroid hair. Sometimes a cross-sectional examina- tion of hair may aid in the identification of race.

Cross-sections of hair from Caucasians are oval to round in shape, whereas cross-sections of Negroid hair are flat to oval in shape. However, all of these observations are general in nature, with many possible exceptions. The criminalist must approach the determination of race from hair with caution and a good deal of experience.

2 M. M. Houk and B. Budowle, “Correlation of Microscopic and Mitochondrial DNA Hair Comparisons,” Journal of Forensic Sciences 47 (2002): 964.

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y The Central Park Jogger Case Revisited On April 19, 1989, a young woman left her apartment around nine p.m. to jog in New York’s Central Park. Nearly five hours later, she was found comatose lying in a puddle of mud in the park. She had been raped, her skull was fractured, and she had lost 75 percent of her blood. When the woman recovered, she had no memory of what happened to her. The brutality of the crime sent shock waves through the city and seemed to fuel a national perception that crime was running rampant and unchecked through the streets of New York.

Already in custody at the station house of the Central Park Precinct was a group of 14- and 15-year-old boys who had been rounded up leaving the park earlier in the night by

police who suspected that they had been involved in a series of random attacks.

Over the next two days, four of the teenagers gave videotape statements, which they later recanted, admitting to participating in the attack. Ultimately, five of the teenagers were charged with the crime. Interestingly, none of the semen collected from the victim could be linked to any of the defen- dants. However, according to the testimony of a forensic ana- lyst, two head hairs collected from the clothing of one of the defendants microscopically compared to those of the victim, and a third hair collected from the same defendant’s T-shirt microscopically compared to the victim’s pubic hair. Besides these three hairs, a fourth hair was found microscopically similar to the victim’s. This hair was recovered from the clothing of Steven Lopez, who was originally charged with rape but not prosecuted for the crime. Hairs were the only pieces of physical evidence offered by the district attorney to directly link any of the teenagers to the crime. The hairs were cited by the district attorney as a way for the jury to know that the videotaped confessions of the teenagers were reliable. The five defendants were convicted and ultimately served from 9 to 13 years.

Matias Reyes was arrested in August 1989, more than three months after the jogger attack. He pleaded guilty to mur- dering a pregnant woman, raping three others, and committing a robbery. He was sentenced to 33 years to life. In January 2002, Reyes confessed to the Central Park attack. Follow-up tests revealed that Reyes’s DNA compared to semen recovered from the jogger’s body and her sock. Other DNA tests showed that the hairs offered into evidence at the original trial did not come from the victim, and so could not be used to link the teenagers to the crime as the district attorney had argued.

After an 11-month reinvestigation of the original charges, a New York State Supreme Court judge dismissed all the con- victions against the five teenage suspects in the Central Park jogger case.

A courtroom sketch of the trial proceeding in the Central Park Jogger case. AP Wide World Photos

CAN THE AGE AND SEX OF AN INDIVIDUAL BE DETERMINED FROM A HAIR SAMPLE? The age of an individual cannot be learned from a hair examination with any degree of certainty except with infant hair. Infant hairs are fine, are short in length, have fine pigment, and are rudimentary in character. Although the presence of dye or bleach on the hair may offer some clue to sex, present hairstyles make these characteristics less valuable than they were in the past. The recovery of nuclear DNA either from tissue adhering to hair or from the root struc- ture of the hair will allow a determination of whether the hair originated from a male or female (see page 275).

IS IT POSSIBLE TO DETERMINE WHETHER HAIR WAS FORCIBLY REMOVED FROM THE BODY? A microscopic examination of the hair root may establish whether the hair fell out or was pulled out of the skin. A hair root with follicular tissue (root sheath cells) adhering to it, as shown in Figure 13–7, indicates a hair that has been pulled out either by a person or by brushing or comb- ing. Hair naturally falling off the body has a bulbous-shaped root free of any adhering tissue. How- ever, the absence of sheath cells cannot always be relied on for correctly judging whether hair has been forcibly pulled from the body. In some cases the root of a hair is devoid of any adhering tissue even when it has been pulled from the body. Apparently, an important consideration is how quickly

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the hair is pulled out of the head. Hairs pulled quickly from the head are much more likely to have sheath cells compared to hairs that have been removed slowly from the scalp.3

ARE EFFORTS BEING MADE TO INDIVIDUALIZE HUMAN HAIR? As we learned in Chapter 11, forensic scientists are routinely isolating and characterizing individual variations in DNA. Forensic hair examiners can link human hair to a particular individual by characterizing the nuclear DNA in the hair root or in follicular tissue adhering to the root (see Figure 13–7). Recall that the follicular tag is the richest source of DNA associated with hair. In the absence of follicular tissue, an exam- iner must extract DNA from the hair root. The growth phase of hair (see page 324) is a useful pre- dictor of the likelihood of successfully typing DNA in human hair.4 Examiners have a higher rate of success in extracting DNA from hair roots in the anagen phase or from anagen-phase hairs entering the catagen phase of growth. Telogen-phase hairs have an inadequate amount of DNA for success- ful typing. Because most hairs are naturally shed and are expected to be in the telogen stage, these observations do not portend well for hairs collected at crime scenes. However, some crime scenes are populated with forcibly removed hairs that are expected to be rich sources for nuclear DNA.

When a questioned hair does not have adhering tissue or a root structure amenable to the iso- lation of nuclear DNA, there is an alternative—mitochondrial DNA. Unlike the nuclear DNA described earlier, which is located in the nuclei of practically every cell in our body, mitochon- drial DNA is found in cellular material outside the nucleus. Interestingly, unlike nuclear DNA, which is passed down to us from both parents, mitochondrial DNA is transmitted only from mother to child. Importantly, many more copies of mitochondrial DNA are located in our cells as compared to nuclear DNA. For this reason, the success rate of finding and typing mitochondrial DNA is much greater from samples, such as hair, that have limited quantities of nuclear DNA. Hairs 1–2 centimeters long can be subjected to mitochondrial analysis with extremely high odds of success. This subject is discussed in greater detail in Chapter 11.

CAN DNA INDIVIDUALIZE A HUMAN HAIR? In some cases, the answer is yes. As we learned in Chapter 11, nuclear DNA produces frequency of occurrences as low as one in billions or tril- lions. On the other hand, mitochondrial DNA cannot individualize human hair, but its diversity within the human population often permits exclusion of a significant portion of a population as potential contributors of a hair sample. Ideally, the combination of a positive microscopic comparison and an association through nuclear or mitochondrial DNA analysis provides a strong and meaningful link between a questioned hair and standard/reference hairs. However, a word of caution: mitochondrial DNA cannot distinguish microscopically similar hairs from different individuals who are maternally related.

Collection and Preservation of Hair Evidence When questioned hairs are submitted to a forensic laboratory for examination, they must always be accompanied by an adequate number of standard/reference samples from the victim of the crime and from individuals suspected of having deposited hair at the crime scene. We have learned that

FIGURE 13–7 Forcibly removed head hair, with follicular tissue attached.

3 L. A. King, R. Wigmore, and J. M. Twibell, “The Morphology and Occurrence of Human Hair Sheath Cells,” Journal of the Forensic Science Society 22 (1982): 267.

4 C. A. Linch et al., “Evaluation of the Human Hair Root for DNA Typing Subsequent to Microscopic Comparison,” Journal of Forensic Sciences 43 (1998): 305.

mitochondrial DNA DNA present in small structures (mitochondria) outside the nucleus of a cell; mitochondria supply energy to the cell; this form of DNA is inherited maternally (from the mother)

nuclear DNA DNA present within the nucleus of a cell; this form of DNA is inherited from both parents

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hair from different parts of the body varies significantly in its physical characteristics. Likewise, hair from any one area of the body can also have a wide range of characteristics. For this reason, the questioned and standard/reference hairs must come from the same area of the body; one can- not, for instance, compare head hair to pubic hair. It is also important that the collection of standard/reference hair be carried out in a way to ensure a representative sampling of hair from any one area of the body.

Forensic hair comparisons generally involve either head hair or pubic hair. Collecting 50 full- length hairs from all areas of the scalp normally ensures a representative sampling of head hair. Likewise, a minimum collection of 24 full-length pubic hairs should cover the range of charac- teristics present in this type of hair. In rape cases, care must first be taken to comb the pubic area with a clean comb to remove all loose foreign hair present before the victim is sampled for standard/reference hair. The comb should then be packaged in a separate envelope.

Because a hair may show variation in color and other morphological features over its entire length, the entire hair length is collected. This requirement is best accomplished by either pulling the hair out of the skin or clipping it at the skin line. During an autopsy, hair samples are collected from a victim of suspicious death as a matter of routine. Because the autopsy may occur early in an investigation, the need for hair standard/reference samples may not always be apparent. How- ever, one should never rule out the possible involvement of hair evidence in subsequent inves- tigative findings. Failure to make this simple collection at an opportune time may result in complicated legal problems at a later date.

Types of Fibers Just as hair left at a crime scene can serve as identification, the same logic can reasonably be extended to the fibers that compose our fabrics and garments. Fibers may become important evidence in incidents that involve personal contact—such as homicide, assault, or sexual

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> > > > > > > > > > > > > > > > > The murder of Ennis Cosby, son of entertainer Bill Cosby, at first appeared unsolvable. It was a ran- dom act. When his car tire went flat, he pulled off the road and called a friend on his cellular phone to ask for assistance. Shortly thereafter, an assailant demanded money and, when Cosby didn’t re- spond quickly enough, shot him once in the tem- ple. Acting on a tip from a friend of the assailant, police investigators later found a .38 revolver wrapped in a blue cap miles from the crime scene. Mikail Markhasev was arrested and charged with murder. At trial, the district attorney introduced firearms evidence to show that the recovered gun had fired the bullet aimed at Cosby. However, a sin- gle hair also recovered from the hat dramatically linked Markhasev to the crime. Los Angeles Police Department forensic analyst Harry Klann identified six DNA markers from the follicular tissue adhering to the hair root that matched Markhasev’s DNA. This particular DNA profile is found in one out of 15,500 members of the general population. Upon hearing all the evidence, the jury deliberated and convicted Markhasev of murder.

Bill Cosby and his son Ennis Cosby. Courtesy Andrea Mohin, The New York Times

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