Chapter 7: Pathology

7.1: Pathology

• Pathologist – a medical doctor who studies and diagnoses disease in humans.
• Forensic Pathologist – a pathologist who has studied not only disease but also trauma (wounds and damage) that leads to the death of an individual.
• Modern Autopsy – involves the standardized dissection of a corpse to determine the cause and manner of death.
  • These are done to help solve a murder, however, are different in many ways, such as who conducts them, when and how they are conducted, and what purpose they serve to society.

Cause and Manner of Death

• The cause of death is divided into primary and secondary causes of death.

  1. Primary Cause of Death – or the immediate cause of death, is a three-link causal chain that explains the cessation of life starting with the most recent condition and going backward in time.
  2. Secondary Cause of Death – includes conditions that are not related to the primary cause of death but contribute substantially to the individual’s demise, such as extreme heat or frigid temperatures, are typically listed.

• Hospital Autopsy – conducted based on a doctor’s request and the family’s permission. If the family denies the request for personal or religious reasons, the autopsy is not performed.

• Medico-legal autopsy – performed under a medical investigation of death for legal purposes.

• Manner of Death – how the causes of death came to be.

  • Generally, there are only four MODs — homicide, suicide, accidental, and natural.

Coroners and MEs

• Coroner – examines all bodies before burial and appraises all wounds, bruises, and other signs of possible foul play.

  • ^^Thomas Baldridge^^ – first American coroner.
  • The position of coroner can be appointed or elected, and typically no formal education or medical training is required. Today, many coroners are funeral directors, who get possession of the body after the autopsy. This can be a major source of income for such officials.

• Medical Examiner – typically a physician who has gone through four years of university, four years of medical school, four years of basic pathology training (residency), and an additional one to two years of special training in forensic pathology. These positions are appointed.

7.2: Postmortem Examination

External Examination

• The Visual Examination of a body starts with a careful description of the deceased’s clothing, photographs (including close-ups) of the body both clothed and unclothed, and a detailed examination of the entire body.

Classification of Trauma

• Mechanical Trauma:
  • Occurs when the force applied to a tissue, such as skin or bone, exceeds the mechanical or tensile strength of that tissue.
  • Sharp force trauma – injuries caused by sharp implements, such as knives, axes, or ice picks.
    • It produces incised wounds.
  • Blunt force trauma – is caused by dull or non-sharpened objects, like baseball bats, bricks, or lamps.
    • It produces lacerations.
  • Contusion – accumulation of blood in the tissues outside the normal blood vessels and is most often the result of blunt impact.
  • Hematoma – a blood tumor or a contusion with more blood.
  • Asphyxia – a type of mechanical trauma in which the body is deprived of oxygen.
    • Suffocation – occurs by covering the nose and mouth, and blockage of the major airways with a foreign object.
    • Strangulation – occurs by manual or ligature compression of the structures of the neck, often leaving characteristic physical evidence, such as the fracture of the hyoid bone and bruising.
    • Chemical Asphyxiation – occurs when the oxygen in the air is replaced by some other gas, such as carbon monoxide (CO).
• Gunshot wounds:
  • The projectile from a discharged firearm produces a special kind of blunt force trauma.
  • Deaths due to firearms (handguns, rifles, and shotguns) are a commonly encountered entity where they form the bulk of homicidal and, to a lesser degree, suicidal manners of death.
• Chemical Trauma:
  • Damage and death results from the interaction of chemicals with the human body.
• Thermal Trauma:
  • Hypothermia – too much exposure to cold.
  • Hyperthermia – exposure to excessive heat.
• Electrical Trauma:
  • Electricity can cause death by several means.
  • Circuits of alternating current at low voltages that cross the heart cause ventricular fibrillation — a random quivering that does not pump the blood through the body properly.
  • Rigor Mortis – the stiffening of the body after death due to the membranes of muscle cells becoming more permeable to calcium ions.
  • Livor Mortis – also known as postmortem lividity, is the settling of blood due to gravity after the heart no longer circulates it through the body; resulting in a purplish discoloration in the skin.
  • Petechiae – pinpoint hemorrhages found around the eyes, the lining of the mouth and throat, as well as other areas often seen in hanging or strangulation victims.
• Other Evidence Collected
  • Smears – a mark or streak of a greasy or sticky substance; where the collected fluid on each swab is wiped across a separate clean glass microscope slide.
  • Any ligatures, such as electrical cords, ropes, or duct tape, are extensively photographed, sketched, and then collected.

Internal Examination and Dissection

• Virchow Method — removing the internal organs, either all together or individually; each organ is removed, examined, weighed, and sampled separately to isolate any pathologies or evidence of disease.

• Virtopsy – a visualizing scanner system that allows for multimodal viewing of a body, both internally and externally, for autopsy purposes. It provides computed tomography, magnetic resonance, 3D surface scanning, and 3D photogrammetry. This technology provides full documentation of the examination, allowing for an observer-independent review of what is normally a one-time event.

Determining the Postmortem Interval

Following death, numerous changes occur that ultimately lead to the dissolution of all soft tissues. The importance of these changes to the forensic pathologist is that they provide a sequence of events that may allow an estimate of the time since death ensued. This determination is based on the principle of sequential changes called the postmortem clock.

The evaluation may include the following phenomena:

• Changes evident upon external examination of the body, such as temperature, livor, rigor, and decomposition;
• Chemical changes in body fluids or tissues;
• Physiological changes with progression rates, such as digestion;
• Survival after injuries, based on the nature, severity, and other factors such as blood loss.

Decomposition of the body begins almost immediately after death and consists of two parallel processes:

• Autolysis — the disintegration of the body by enzymes released by dying cells; and
• Putrefaction — the disintegration of the body by the action of microorganisms, such as bacteria.

7.3: Laboratory Analysis

Histology

• The pathologist typically requests a histology examination for evidence of cellular pathologies resulting from disease, trauma, or preexisting conditions.
  • Small samples of the tissues of interest are taken, embedded in plastic, and sectioned using a microtome — (a machine that makes very thin, very precise slices) to a thickness of only a few microns.
• A medical technologist or histologist will then examine the sections microscopically, write a report, and pass this along to the pathologist.

Toxicology

• Toxicology Screen – tests that help the forensic toxicologist determine the absence or presence of drugs and their metabolites, chemicals such as ethanol and other volatile substances, carbon monoxide and other gases, metals and other toxic chemicals in human fluids and tissues.
• Society of Forensic Toxicologists, Inc. (SOFT) – an organization composed of practicing forensic toxicologists and those interested in the discipline for the purpose of promoting and developing forensic toxicology.

Autopsy Report

• The autopsy report is a crucial piece of information in a death investigation.

• Because the results of an autopsy, hospital, or medico-legal, may end up in court, certain basic and specific information must be included in every autopsy file, such as:

  • Police report,
  • Medical investigator report,
  • Witness report
  • Medical history of the decedent.

• Exhumation – the action of digging up something buried, especially a corpse.

  • If questions about the cause or manner of death arise once the deceased is buried, exhumation must be performed.

• Embalming – a process of chemically treating the dead human body to reduce the presence and growth of microorganisms, retard organic decomposition, and restore an acceptable physical appearance.

  • Formaldehyde – also known as formalin; is the main chemical used to preserve the body. These chemicals are highly reactive and can alter or mask drugs or poisons in the body at the time of death.

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