After studying this chapter you should be able to: Describe the role of the forensic pathologist
Describe the external, internal, and toxicology phases of an autopsy
Distinguish cause and manner of death
Describe common causes of death
List various categories associated with the manner of death
Describe chemical and physical changes helpful for estimating time of death
Discuss the role of the forensic anthropologist in death investigation
Describe the role of the forensic entomologist in death investigation
death investigation
algor mortis autopsy cause of death forensic anthropology forensic entomology forensic pathologist livor mortis manner of death petechiae postmortem interval
(PMI) rigor mortis
KEY TERMS
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Role of the Forensic Pathologist Few investigations bring with them the intense focus of community interest and news media cov- erage as that of a suspicious death. Generally, forensic pathologists associated with the medical examiner’s or coroner’s office are responsible for determining the cause of an undetermined or unexpected death. These officers coordinate their response with that of law enforcement in the ensuing investigation. The titles coroner and medical examiner are often used interchangeably, but there are significant differences in their job descriptions. In the United States, there’s a mix of state medical examiner systems, county medical examiner offices, and county coroner systems. The coroner is an elected official and may or may not possess a medical degree. The term coroner dates back hundreds of years to the rule of King Richard I of England (1189–1199), who created the office of the coroner to collect money and personal possessions from people who had died. The medical examiner, on the other hand, is almost always an appointed official and is usually a physician who generally is a board-certified forensic pathologist and is responsible for certifying the manner and the cause of a death.
The tasks of examining the case for the cause and manner of death and recording the results on a death certificate are the responsibilities of both offices. However, although both the coro- ner’s office and the medical examiner’s office are charged with investigating suspicious deaths, only the pathologist is trained to perform an autopsy. Ideally, the coroner or medical examiner’s office should be staffed with physicians who are board certified in forensic pathology and should charge them with determining the cause of death by autopsy. The cause-of-death determination, however, involves not just an autopsy but also the history of death, witness statements, relevant medical records, and any scene investigation, all of which constitute the surrounding circum- stances of death.
From a practical point of view, it is often not feasible for the forensic pathologist to per- sonally solicit information regarding the circumstances surrounding a death or to respond in person to every death scene. Thus, the gathering of vital information and the scene investigation can be delegated to trained coroner/medical examiner investigators who, when a crime scene is involved, coordinate their efforts with the those of crime-scene and criminal investigators. The forensic pathologist’s work is also aided by the skills of specialists including forensic anthro- pologists, forensic entomologists, and forensic odontologists.
Scene Investigation With regard to any scene investigation, protection of the overall scene and the body are of para- mount importance, as is the ultimate removal of the body in a medically acceptable manner. The death investigation involves documenting and photographing the undisturbed scene; collecting relevant physical evidence; attempting to determine time of death, which must be done in a timely fashion at the scene; and, among other things, ascertaining premortem locations of the body and whether any postmortem movement of the body occurred. Examples of observations that can be made of the body at the scene include bruises along the upper lip, which may be evi- dence of smothering; a black eye limited to the eyelids, which implies an injury from inside the head; or bleeding from the ear, which implies a basal skull fracture.
A critical phase of the death investigation will be a preliminary reconstruction of events that preceded the onset of death, so all significant details of the scene must be recorded. Blood spatter and blood flow patterns must be documented. Blood should be sampled for testing in case some of the blood was cast off by a perpetrator. Any tire marks or shoe prints must be documented. Fingerprints must be processed and collected. Of particular importance is the search for any evi- dence discarded, dropped, or cast off by a perpetrator. When a weapon is involved, there must be a concerted effort to locate and recover the suspect weapon. In the case of firearm deaths, fired bullets or casings must be found and their locations documented. In such firearm deaths, before the body is moved or clothing is removed, blood spatter directionality and trace evidence (such as hairs) on the hands must be documented. Paper bags then should be placed over the hands and secured around the wrist or arm (paper prevents moisture condensation) to preserve any ad- ditional evidence.
Photographs must always be taken before the scene is altered in any way (except from lifesaving efforts). This includes moving the body or anything on the body, such as clothing or jewelry. A particularly violent scene can carry with it a large amount of blood and disorder.
forensic pathologists Investigative personnel, typically medical examiners or coroners, who investigate the cause, man- ner, and time of death of a victim in a crime; can also be a physician who has been trained to conduct autopsies.
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Blood may be found at different locations throughout the scene. This could prove to be important in shaping the events that led to the final outcome; it may be possible to determine the initial location of the injury, as well as victim and assailant movements throughout the course of events. Initially it may be difficult to properly infer the source of the wounds and the order in which they were received at the scene. Photographs then will play a very large role when reconstructing the events later. As always, photographs should be taken with a scale, always first overall, then at medium range, then close up. The photographer must also be careful not to get caught up in cap- turing the injuries exclusively. Negative findings can also be significant. This means photographs should also be taken of areas on the body where injuries are not apparent.
Protection of the body and the overall scene is of paramount importance, as is the ultimate removal of the body in a medically acceptable manner. Often the initial phase of the investiga- tion will focus on determining the identity of the deceased, often called the decedent. Although this task may be relatively simple to accomplish through a visual examination, complications can arise. Body decomposition and the existence of extensive trauma can complicate the identi- fication. This may necessitate the application of more sophisticated technology, such as DNA, fingerprinting, dental examination, and facial reconstruction.
The Autopsy An autopsy, in its broadest definition, is simply the examination of a body after death (i.e., a postmortem examination). The autopsy can be further described as one of two types: a clinical/ hospital autopsy or a forensic/medicolegal autopsy. The clinical/hospital autopsy focuses on the internal organ findings and medical conditions. Its purpose is to confirm the clinical diagno- ses, the presence and extent of disease, any medical conditions that were overlooked, and the appropriateness and outcome of therapy. In contrast, the goal of a forensic/medicolegal autopsy is to determine the cause of death and confirm the manner of death, often to be used in crimi- nal proceedings. The forensic autopsy usually emphasizes external and internal findings while developing meaningful forensic correlations between sustained injuries and the crime scene (see Figures 5–1 and 5–2).
All the steps of the forensic autopsy must be carefully documented and photographed. The documentation should include date, time, place, by whom the autopsy was performed, and who attended the autopsy. Photographs of the injuries, complete with a scale, and descriptions of
autopsy A surgical procedure performed by a pathologist on a dead body to ascertain—from the body, organs, and bodily fluids—the cause of death.
FIGURE 5–1 An autopsy suite.
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each photograph’s location are important when correlating external wounds with internal dam- age. Negative photographs—photographs of uninjured parts of the body—are also important. The autopsy report and photographs are so important because, once the body is buried, no further evidence can be collected and no additional findings can occur.
EVIDENCE FROM THE AUTOPSY The search for physical evidence must extend beyond the crime scene to the autopsy room of a deceased victim. Here, the medical examiner or pathologist carefully examines the victim to establish the cause and manner of death. As a matter of routine, tissues and organs are retained for pathological and toxicological examination. At the same time, arrangements must be made between the examiner and investigator to secure a variety of items that may be obtainable from the body for laboratory examination. The following are among the items to be collected and sent to the forensic laboratory:
Buccal swab (for DNA typing purposes)
– ing from touching or saliva
These items of evidence should be properly packaged and labeled like all other evi- dence. Once the body is buried, efforts at obtaining these items may prove difficult or futile. Furthermore, a lengthy time delay in obtaining many of these items will diminish or destroy their forensic value.
EXTERNAL EXAMINATION The forensic autopsy consists of an external examination and an internal examination. The first steps taken for the external examination include a broad overview of the condition of the body and the clothing. Obvious damage to the clothing should be matched up to injuries on the body. General characteristics of the body should be noted, including sex, height, weight, approximate age, color of hair, and physical condition.
FIGURE 5–2 Tools used for an autopsy.
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The presence of tattoos and scars, as well as puncture and track marks, are noted. All evidence of apparent medical intervention must be carefully noted, described, and photographed because occasionally these may be misinterpreted, especially chest tube insertions and emergency cardiac punctures. The mouth and nose are examined for the presence of vomit and/or blood and trace evidence, and the ears are examined for blood. Any irritations in the nasal cavity can be indicative of drug sniffing.
Often, paper bags are placed over the hands at the crime scene until it is time to exam- ine them. This prevents contamination and possible loss of trace evidence, such as hairs and fibers. This preservation of evidence can play an important role in identifying a suspect. A victim will sometimes have skin and DNA under his or her fingernails from fighting with the assailant.
The external examination also consists of classifying the injuries. This includes distinguish- ing between different types of wounds, such as a stab wound versus a gunshot wound. The inju- ries that are examined may include abrasions, contusions, lacerations, and sharp-injury wounds. Hemorrhages in the eyelids (petechiae) are also essential to note, as they can indicate strangula- tion. Attention is also paid to the genitalia, especially in cases where sexual abuse is suspected. In these cases, vaginal, oral, and rectal samples are taken.
The discharge from a firearm will produce characteristic markings on the skin. This dis- charge is a combination of soot and gunpowder. It will leave markings called stippling or tattoo- ing around the bullet hole. The stippling can be analyzed in terms of its span and density in order to approximate the range of fire. The range of fire may prove to be the most important factor in distinguishing a homicide from a suicide.
X-ray examinations can be very useful in the autopsy process. They are most commonly performed in gunshot wound cases and stab wound cases. Even if the bullet, knife, or other piercing weapon is recovered outside the body, an X-ray will identify any fragments still inside the body. An X-ray will also help determine the path of the projectile or sharp utensil. X-rays can also be very helpful in cases where the victim was beaten, especially situations in which the victim is a child: an X-ray can show past bone fractures and a possible pattern of abuse.
INTERNAL EXAMINATION The dissection of the human body generally entails the removal of all internal organs through a Y-shaped incision beginning at the top of each shoulder and extending down to the pubic bone. Performing the internal examination entails weighing, dissecting, and sectioning each organ of the body. When required and in accordance with jurisdictional rules, microscopic examination of the sectioned organs is conducted, which can help in determining the cause of death. For example, microscopic examination of lungs and liver can confirm chronic intravenous drug abuse. Examination of the cranium requires cutting an incision from behind one ear to the other, peeling the scalp upward and backward, and sawing the skull in a circular cut; then the skull cap is removed to reveal the brain, as shown in Figure 5–3.
Special care is taken to identify any preexisting conditions or malformations in the organs that might have contributed to the death of the victim. Pulmonary edema (fluid accumulation in the lungs) is frequently found in victims of chronic cocaine and amphetamine abuse. Heart malformations may cause sus- picious death in an otherwise healthy individual.
Special attention is paid to the digestive tract if poison- ing is suspected. The stomach can show partially digested or dissolved pills. Chemical analyses can also be carried out to show signs of poisoning. The amount of pills or tablets in the stomach can aid in the determination of manner of death as well. It is not always a sure sign, but typically it is unlikely that a person will accidentally swallow a large number of pills. This would suggest suicide rather than an accidental overdose. Stomach contents may reveal the deceased’s last meal. The extent of digestion can help with determining the time of death.
FIGURE 5–3 A brain during autopsy.
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TOXICOLOGY The internal examination is also where toxicological specimens are taken. These include samples of blood, stomach content, bile, and urine. All bile in the gallbladder and all stomach content are collected. In addition to these, brain matter, liver, and vitreous humor are also gathered. These specimens can play especially large roles in cases where poisoning or drug abuse is suspected.
Blood is often tested to determine the presence and levels of alcohol and drugs. Blood should be taken from areas of the body where there is the least chance of contamination. Blood should never be collected from body cavities, where it may be contaminated from adjacent structures. Many changes occur in the body after death, and these changes can alter the drugs present in the system at the time of death. This can make interpreting how much of a drug was present, if any at all, a very challenging task. Some drugs redistribute or reenter the blood after death and thus may complicate the interpretation of postmortem blood levels of these drugs. This phenomenon is known as postmortem redistribution. For this reason, it is best to collect blood at distant areas of the body to allow the toxicologist to compare the agreement of the drug concentrations found. The ideal location to retrieve the blood is internally, directly from the inferior vena cava (the large vein inside the lower abdominal region, which receives its blood from the femoral veins) using a syringe. Where postmortem redistribution of drugs may have occurred, blood should also be collected at autopsy from the superior venous system directly above the heart.
For illicit as well as legal substances, it is necessary to know what levels are indicative of therapeutic use and what levels indicate toxicity of a given substance. Much information regard- ing therapeutic versus toxic drug levels has been published. This data can help pathologists and toxicologists ascertain the cause of death. Most drug-related deaths are quite apparent from the blood concentrations of alcohol and/or a drug found in the postmortem toxicological report. (Note that depressant drugs will act in concert with alcohol.) However, in some cases of drug- induced death, drug levels may not always provide evidence. Cocaine is a prime example of this. Cocaine-induced sudden death is an event with an incubation period. Structural alterations of the cardiovascular system are required, and such alterations take months, or perhaps years, of chronic cocaine use. In these individuals, death and toxicity may occur after the use of even a trivial amount of the drug.
Unlike drug analyses, general testing for poisons is not a routine procedure carried out by the pathologist. However, if a specific poison is suspected, a particular test must be performed. A body that displays a cherry-red discoloration often leads a pathologist to suspect carbon monoxide poisoning. The pathologist would then perform a toxicological test of the blood. Poisoning by cyanide could also produce a pinkish discoloration. Often, cyanide toxicity will show additional signs, such as a distinct smell of burnt almonds. Corrosion around the lips of a victim may lead to a suspicion of ingesting an acid or alkaline substance.
Cause of Death A primary objective of the autopsy is to determine the cause of death. The cause of death is that which initiates the series of events ending in death. The most important determination in a violent death is the character of the injury that started the chain of events that resulted in death. However, if the sequence of events leading to death is sufficiently prolonged, then the decedent may actu- ally suffer from adverse medical conditions brought about by the initial injury and then die as a result of those conditions. In that case, it will be up to the forensic pathologist to determine that the original injury inflicted on the victim was the underlying cause of death. Some of the more common causes of death are discussed here.
BLUNT-FORCE INJURY A blunt-force injury is caused by a nonsharpened object such a bat or pipe. A blunt-force injury can abrade, or scrape, tissue. If tissue is crushed by a blunt force to the point of causing skin to overstretch, a laceration will form, characterized by the skin splitting and tearing. Lacerations exhibit abrasions around the open wound, tissue bridging within the open wound, and torn or disturbed tissue beneath the skin surrounding the open portion of the wound. Blunt-force injury can also crush tissue. This will cause bleeding from tiny ruptured blood vessels within and beneath the skin, known as a contusion, or bruise (see Figure 5–4). Much has been written about determining the age of bruises, but forensic pathologists have become keenly aware that attempting to “age” bruises based on color and changes in color over time is fraught with
WEBEXTRA 5.1 See How an Autopsy Is Performed
cause of death Identifies the injury or disease that led to the chain of events resulting in death.
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difficulty, and contusions must be interpreted with great care and reserve. Some contusions only become visible externally over time, and frequently, bruises will not be visible externally but become eminently visible internally within soft tissues (e.g., in the abdomen and on the back, arms, and legs).
A contusion can sometimes exhibit the pattern of the weapon used. For ex- ample, if a person wearing a ring strikes another person, the ring may imprint its pattern onto the skin. A person who stomps on another may leave the impression of his or her shoe heel. Over time, however, the bruise will lose its original shape and pattern and undergo color changes. Some objects will produce a characteris- tic bruised perimeter and a white center.
The outward appearance of the injuries does not always coincide with the injuries sustained inside the body. This is something the pathologist must keep in mind when examining blunt-force injuries. A single blow to certain parts of the body can cause instantaneous death with little visible damage. Likewise, a blow to the head can cause a concussion that can be instantly fatal.
SHARP-FORCE INJURIES Sharp-force injuries occur from weapons with sharp edges, such as knives or blades. These weapons are capable of cutting or stabbing. A cut is formed when the weapon produces an injury that is longer than it is deep. In contrast, a stab is deeper than its length. As shown in Figure 5–5, the tissue associated with these types of wounds is not crushed or torn but sliced.
A scene that involves a sharp-force injury is usually especially bloody and unruly. Blood may be found at different locations throughout the scene. Again, this information may make it possible to determine the initial location of the injury as well as where the body was moved throughout the course of events. Particularly important in sharp-force cases is to examine the victim for defensive wounds. A victim’s forearm that exhibits wounds may indicate defense wounds. These occur when the victim attempts to fight off the attacker or block assaults. Though defense wounds are more typical on the outer fore- arms, they can also be evident on the lower extremities if the victim tries to protect himself or herself by kicking. A lack of any defense wounds can lead a pathologist to conclude that the victim was either unconscious or somehow tied up during the assault.
ASPHYXIA Asphyxia encompasses a variety of conditions that involve interference with the intake of oxygen. For example, death at a fire scene is caused primarily by the extremely toxic gas carbon monoxide. When carbon monoxide is present, hemoglobin, the protein in red blood cells that transports oxygen, will bind to the carbon monoxide instead of oxygen. This is carbon monoxide poisoning, and this deadly complex of hemoglobin and carbon monoxide is known as carboxyhemoglobin. Bound up with carbon monoxide, the hemoglobin is prevented from transporting oxygen throughout the body, causing asphyxia. High levels of carbon monoxide in the blood will cause death. Low levels of carbon monoxide can cause a victim to become disoriented and lose consciousness.
Carbon monoxide will not continue to build up in the body after death. The levels found in a fire victim then can be used to determine whether the individual was breathing at the time of the fire. The presence of soot is an- other indicator that the victim was alive during the fire. These black particles are often seen in the airway of fire victims who inhaled smoke before death. During the autopsy, soot can be observed, especially in the larynx and trachea and even in the lungs. Sometimes the victim will actually swallow the soot. In these cases, traces can be found in the esophagus and the lining of the stomach.
The ultimate cause of a death from hanging is typically the cessation of –
chiae on the eyelids, along with a swollen and a blue/purplish appearance of
FIGURE 5–5 A stab wound.
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FIGURE 5–4 Bruising (contusions) on the skin.
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the face. Petechiae are very small and are caused by blood having escaped into the tissues as a result of capillaries bursting (see Figure 5–6). Although petechiae are witnessed in hanging cases, they are more common in strangulation deaths. Typically the hyoid bone (the bone on which the tongue rests) and thyroid cartilage (located below the hyoid) are not fractured in cases of hanging. A break of the thyroid cartilage is common, however, in manual strangulation cases.
In hangings it is vitally important to document exactly how the victim was initially found and the position of the encircling noose, as shown in Fig- ure 5–7. The type of knot used may strongly support the notion that another person was involved in the hanging. This means that the knot should always be preserved for later examination. Either the noose should be slipped off the victim’s head intact, or the noose should be cut distant from the knot. Defense wounds are common on strangulation victims. Often the marks found on the neck of a victim are the victim’s own, made in the attempt to loosen whatever was constricting his or her neck. Even in cases of hanging by suicide, there can be defensive wounds on the neck.
Smothering can occur by various materials that block the mouth, nose, and internal airway. Pillows or a hand can inhibit breathing. Gags that are used to silence a victim can be sucked into the airway and block oxygen flow. Typically a death by smothering is homicidal in nature. Accidental smother- ing usually occurs only in infants or in cases where a victim is trapped under an obstruction.
GUNSHOT WOUNDS When evaluating a gunshot wound, the estimated range of fire is one of the most important characteristics to analyze (see Figure 5–8). The appearance of the wound can help in estimating whether the firearm used to inflict the wound was discharged while in contact with the victim’s body or from a distance of only inches to many feet away (see Figure 5–9). The investigator will compare powder residue distribution around the wound to test fires collected from the inflicting firearm to make this estimate. Obviously if the firearm was fired at a distance of several feet, suicide is a highly unlikely cause of death because the wound could not have been self- inflicted. Gunpowder residue on the victim’s is a possible indicator of suicide, but this is not always the case. Evidence of contact shots, that is, shots fired with the gun held against the body of the victim, typically indicates that the death was not an accident. The autopsy must include a determination of the path or “wound track” of the projectile. The wound track is determined by observing the wound from the outside of the body, following the track of the projectile through the body, and documenting its terminus. The pathologist will recover any and all projectiles from the body, carefully protecting the forensic markings. The autopsy of gunshot victims should include several facts in addition to the general autopsy facts; scene investigation and the results of toxicological and serological analyses are important. All findings regarding the bullet wounds should be noted, as well as descriptions of the clothing. The police report with a thorough description of the scene is also important.
A gunshot wound may not necessarily explain why a victim died. A person who sustains a gunshot wound can bleed to death in a matter of minutes or up
to several hours. Infection can also be a contributory cause of death, especially in cases where the victim was shot in the abdomen; he or she might live several days but eventually succumb to infection. In cases where the victim was shot in the head but survives in a comatose state, pneu- monia often develops. These intervening factors are considered contributory causes of death, but the gunshot wound is still considered the underlying cause of death.
SUBSTANCE ABUSE Drug abuse continues to be an enormous problem in the United States. Drug enforcement is a multibillion-dollar industry. Many of the abused drugs in the country are illegal, but not all are. Deaths as a result of substance abuse are common cases that a forensic pathologist must face. Because drug abuse is so common, the forensic pathologist will routinely test for the presence of drugs in nearly all investigations, and routine tests are available for many commonly abused drugs. As technology has improved, many drugs can be detected at very
petechiae Pinpoint hemorrhaging often observed in the white area of the victim’s eyes; often observed in strangulation cases.
FIGURE 5–7 A ligature pattern on a neck with corresponding ligature.
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FIGURE 5–6 Petechial hemorrhages in a victim’s eye.
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low levels. These factors have helped considerably in making substance abuse testing easier and less expensive.
Drug abuse can directly cause death, or it can cause complications that can serve as a contributing factor to death. An abuser can misuse a drug or a number of drugs for years, accumulating detrimental effects in that time. Death as a result of those effects is typically labeled a natural death by the pathologist. Drugs can also alter a person’s judgment and psychomotor skills to the point that a fatal accident occurs. Drugs are also often at the source of acts of violence that result in death.
Manner of Death The manner of death relates to the circumstances that led to the fatal result and is the culmination of the complete investigation, including the determi- nation of cause of death. The certification of the circumstances and man- ner of death is the responsibility of the coroner’s and medical examiner’s offices. The manner in which death occurred is classified in death certifica- tions as one of five categories: homicide, suicide, accidental, natural, or undetermined.
HOMICIDE Although there is no universal agreement on its definition, generally the term homicide, as certified by coroners’ and medical examiners’ offices, is defined as a nonaccidental death resulting from grossly negligent, reckless, or intentional actions of another person. Both the cause and manner of death, as certified by the coroner’s/medical examiner’s offices, can become the subject of expert debate during any subsequent judicial proceedings. However, this does not result in a revision of the death certification unless there has been negligence on the part of the certifying offices.
If the pathologist was unable to go to the scene, he or she should receive adequate information detailing the conditions of the scene from coroner/medical examiner investigators and law enforcement personnel. This information should include how the body was discovered as well as when and where. It is also an important first step for investigators to make note of the algor mortis, livor mor- tis, and/or rigor mortis of the body at the scene. These will help determine time of death.
SUICIDE Suicide is the result of an individual taking his or her own life with lethal intention. For a determination of suicide, it must be demonstrated that the individual carried out the act alone. If there is any doubt about the intentions of the victim, the death is not classified as a suicide; the death is ruled as an accident or even as undetermined. The most common methods of suicide include self-inflicted gunshot wounds, hanging, and drug overdosing. Although drug abuse is deliberately committed by a victim, it is not considered suicide unless it was clearly intended as a lethal act.
homicide. The victim’s personal history, including his or her psychiatric history, becomes rel- evant. Suicidal threats or past attempts would give obvious evidence of a suicide as opposed to an accident. In all cases of suspected suicide, a thorough search of the victim’s possessions should be made to locate a suicide note.
Multiple gunshot wounds might lead one to suspect homicide. However, a person who is committed to ending his or her own life may take several shots if the wounds are not instantly fatal. It is imperative to confirm that it is physically possible that the victim could inflict the wounds. There are a few areas of the body that strongly point toward homicide. These are areas that are not easily accessible to the victim’s own reach. For example, anywhere on the back of a victim is difficult and sometimes impossible for the victim to have shot by his or her own hand. This is especially true if the wound was made in the back of the head. For suicides, the most common shot is to the temple of the head. The mouth, forehead, and chest are also common.
FIGURE 5–9 A gunshot entrance wound to the head from a weapon fired several inches from the target.
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FIGURE 5–8 A contact gunshot wound to the temple of a suicide victim.
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to manner of death A determination made by a forensic pathologist of the cause of death. Five broad categories are homicide, suicide, accidental, natural, and undetermined.
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Also, if the wound was immediately incapacitating, the weapon should be present. Blood spatter analysis should be consistent with the proposed order of events. All victims involved in gunshot cases should have their hands swabbed for gunshot residue.
ACCIDENTAL In all deaths that are ruled accidental, there must not be intent to cause harm through gross negligence on the part of a perpetrator or the victim. Traffic accidents make up a large percentage of accidental deaths, followed by drug overdoses and drownings. The surviving driver may have vehicular homicide charges brought against him or her, especially if the driver is determined to have been driving under the influence of drugs or alcohol. In this case, the official manner of death certified on the death certificate in many jurisdictions would be vehicular homicide.
All cases that have the possibility of being a ruled an accident should have toxicological analyses carried out. The presence of drugs and/or alcohol in the victim’s system can poten- tially affect the determination. Also, the pathologist should be aware that some events might be disguised as accidents to cover up a homicide or suicide. For example, bodies recovered from a house fire might show evidence that the victims were dead before the fire started. This evidence might include a lack of soot in the victims’ airways or no indication of elevated levels of carbon monoxide. This scenario, although not common, illustrates how the autopsy and scene can appar- ently not correlate with each other. No matter how obvious a scene may appear, the two should always correspond with one another. Cases of electrocution are generally ruled as accidents, but this may be difficult to prove. High-voltage electrocutions will usually leave burns on the body. Low-voltage electrocutions, however, may show few or no signs of trauma. The scene then be- comes crucial in ascertaining the events surrounding the death.
The determination of manner of death in drownings (accidental, suicidal, or homicidal), falls (accidental, pushed, or deliberate), and asphyxiations can be exceedingly difficult, and therefore the investigation into all of its components becomes much more important than the autopsy.
NATURAL CAUSES The differentiation between the categories of manner of death can be difficult to make. The distinction between natural and accidental deaths can pose challenges. The classification of natural death includes disease and continual environmental abuse. This abuse can encompass various events, such as chronic drug and alcohol abuse or longtime exposure to natural toxins or asbestos. Again, although drug abuse is deliberately committed by the victim, a death caused by drug use is not considered suicide unless it is clear that drugs were taken as an intentionally lethal act. Acute ethanol intoxication can be ruled as either natural or accidental depending on the circumstances. If the victim suffers from chronic alcoholism, the death is ruled to be natural. If the victim is a teenager experimenting with alcohol for the first time, the death is ruled an accident.
UNDETERMINED A death is ruled to be undetermined only when a rational classification cannot be established. This can happen when the mechanism that caused the death cannot be determined by a physical finding at the autopsy or because of the absence of meaningful findings in the subsequent toxicological and microscopic examinations.
Estimating Time of Death A pathologist can never give an exact time of death. However, there are many characteristics that the examiner can analyze in order to arrive at an approximate time of death. Some features can give a very probable time of death, but others are extremely variable. Witnesses can serve to reconstruct the events leading up to the death and the incidents that occurred after the death, along with the times when they occurred, but a single witness’s account alone is not enough to make an accurate determination. The chemical and physical changes that occur after death must also be examined.
ALGOR MORTIS After death the body undergoes a process in which it continually adjusts to equalize with the environmental temperature. This process is known as algor mortis. An algor mortis determination must be performed at the scene as early as possible. The first step is to determine as best as possible what the environmental temperatures may have been prior to discovering the body. Then the environmental temperature and the bilateral axillary and/or ear canal temperatures are recorded at the crime scene (rectal temperatures are usually too disruptive
algor mortis A process that occurs after death in which the body temperature con- tinually cools until it reaches the ambient or room temperature.
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at the scene). The cooling rate of a typical body can be used to estimate the time of death. At average ambient temperatures of 70–72°F, the body loses heat at a rate of approximately of 1–1.5°F per hour until the body reaches the ambient or room temperature. However, the rate of heat loss is influenced by factors such as ambient temperature, the size of the body, and the victim’s clothing. Because of such factors, this method can only approximate the amount of time that has elapsed since death.
LIVOR MORTIS Another condition that begins when circulation ceases is livor mortis. When the human heart stops pumping, the blood begins to settle in the parts of the body closest to the ground. As shown in Figure 5–10, the skin becomes a bluish-purple color in these areas. The onset of this condition begins 20 minutes to 3 hours after death and under average conditions continues for up to 16 hours after death, at which point all lividity, or coloring, is fixed. Initially, lividity can be pressed out of the vessels when the skin is pressed, that is, lividity can be “blanched.” With time, coloring becomes “fixed” in the vessels, beginning in the most dependent (lowest) areas and progressing to the least dependent areas, and then finally no blanching can be elicited anywhere. In any case, levels of lividity are tested at the scene with regard to whether it is completely fixed, blanches when subjected to light pressure, or blanches when subjected to significant pressure. A range of time of death can be estimated if at least some of the lividity is still blanching. However, the environmental temperature and the rate of body temperature decline (i.e., algor mortis) directly affect the rate of fixation of lividity and therefore must be taken into account when attempting to estimate time of death from lividity.
Different lividity patterns in a body may indicate that the body was moved after death but before livor mortis had fully fixed. The skin does not become discolored in areas where the body is restricted by either clothing or an ob- ject pressing against the body. This information can be useful in determining whether the victim’s position was changed after death. Livor that is a deep purple is often seen in cases where the victim suffered asphyxia or heart failure.
RIGOR MORTIS Immediately following death, a chemical change occurs in the muscles that causes them to become rigid, as shown in Figure 5–11. This condition, rigor mortis, evolves over the first 24 hours under average temperature and body conditions. This rigidity subsides as time goes on, however, and disappears after about 36 hours under average conditions. Rigor will develop in the position that the body was in at the time of death, essentially
FIGURE 5–10 Livor mortis.
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livor mortis A medical condition that occurs after death and results in the set- tling of blood in areas of the body closest to the ground.
FIGURE 5–11 Rigor mortis in the arm of a decedent.
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rigor mortis A medical condition that occurs after death and results in the stiff- ening of muscle mass. The rigidity of the body begins within 24 hours of death and disappears within 36 hours of death.
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freezing the body in that pose. Discovering a body in a position that defies gravity is a likely indicator that the body was moved after death.
Although rigor mortis can roughly indicate a time of death, there are factors that can alter this determination. An environment that is hot can speed up the process significantly. Conditions that affected the body before death, such as exercise or physical activity, can also speed up the process. Because rigor mortis occurs as a result of the muscles stiffening, individuals with de- creased muscle mass may not develop rigor completely. Examples of these individuals may be infants or elderly or obese persons.
POTASSIUM EYE LEVELS Another approach helpful for estimating the time of death is to determine potassium levels in the decedent’s ocular fluid, that is, the fluid within the eye, also known as the vitreous humor. It is important to draw a clean, bloodless vitreous sample from one eye with a syringe as soon as possible at the scene, then draw a second sample from the other eye an hour or two later. After death, cells within the inner surface of the eyeball release potassium into the ocular fluid. By analyzing the amount of potassium present at various intervals after death, the forensic pathologist can determine the rate at which potassium is released into the vitreous humor and use it to approximate the time of death. However, the rate of potassium release also is dependent on ambient temperatures.
STOMACH CONTENTS Special attention must be paid to the digestive tract. The identification of food items in the stomach may help determine the location of the decedent prior to death (during his or her last meal). The quantity, consistency, and color of bile, and the degree of digestion of food in the stomach and its passage into the small intestine can help determine the time of death. The stomach also can contain partially digested or dissolved pills. Chemical analyses can be carried out to identify and analyze substances found in the stomach. These can aid in the determination of cause and manner of death.
DECOMPOSITION Once decomposition has set in, the preceding methods of determining time of death are no longer of any use. After death, two decomposition processes take place: autolysis and putrefaction. Autolysis is fundamentally self-digestion by cells’ own enzymes, and its rate varies from organ to organ depending on the mechanism of death, the enzyme content of the respective organs, the position of the body, and environmental factors. Putrefaction is decomposition carried out by microorganisms such as bacteria. Putrefaction is accompanied by bloating, discoloration, and a foul smell caused by accumulating gases. Again, the rate of putrefaction is dependent on the mechanism of death (for example, congestive respiratory versus sudden cardiac death) allowing bacteria to spread from the bowel, presence or absence of infection, environmental temperatures and humidity, degree of obesity, extent of clothing, and so on. Green discoloration often begins in the abdomen. Darker green or purple discoloration follows on the face. The skin begins to blister with gas and then peel (called slippage). The skin of the hands and feet can actually detach and come off the body like a glove. This stage is also accompanied by bloating, which causes the eyes to bulge and the tongue to protrude. The chest and extremities will then turn a green/purple discoloration and bloat.
In the postmortem period of decomposition, a waxy substance called adipocere may form. Adipocere adds a white or gray waxlike consistency to fatty tissues in the face and extremities that can take on a yellow to tan color. Typically, adipocere takes about three months to develop.
Role of the Forensic Anthropologist Forensic anthropology is concerned primarily with the identification and examination of hu- man skeletal remains. Skeletal bones are remarkably durable and undergo an extremely slow breakdown process that lasts decades or centuries. Because of their resistance to decomposition, skeletal remains can provide a multitude of individual characteristics long after a victim’s death. An examination of bones may reveal a victim’s sex, approximate age, race, height, and the nature of a physical injury.
Recovering and Processing Remains Thorough documentation is required throughout the processes of recovery and examination of human remains. A site where human remains are found must be treated as a crime scene (see
forensic anthropology The use of anthropological knowl- edge of humans and skeletal structure to examine and identify human skeletal remains.
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