Forensic science chapter 5 pollen and spore examination

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.