# Forensic Pathology Principles for the Anatomic Pathologist

## Introduction

Forensic pathology applies anatomic pathology principles to medicolegal investigations. While most anatomic pathologists do not practice forensic pathology, understanding the fundamentals of death investigation, wound interpretation, and medicolegal reporting is important for recognizing cases requiring forensic referral and for competent communication with medicolegal authorities.

## Jurisdiction and the Death Investigation System

### Medical Examiner vs. Coroner Systems

A **medical examiner** is an appointed physician, typically a board-certified forensic pathologist, serving in a merit-based system. A **coroner** is an elected or appointed official who may or may not be a physician, with jurisdiction varying by state or county. Both systems investigate **unnatural, sudden, unexpected, or unexplained deaths**. Reportable deaths include homicide, suicide, accident, deaths in custody, deaths during medical procedures, deaths unattended by a physician, and suspicious circumstances.

### Categories of Manner of Death

**Natural** death results solely from disease processes. **Accident** results from unintentional injury. **Suicide** results from intentional self-harm. **Homicide** results from the actions of another person (a legal determination, not necessarily criminal). **Undetermined** is assigned when there is insufficient evidence to classify the manner of death. Manner of death is a **medicolegal opinion**, distinct from cause of death.

| Manner of Death | Definition | Key Points |
|---|---|---|
| Natural | Disease process only | No external contributing factors |
| Accident | Unintentional injury | Includes drug overdose, falls, MVA |
| Suicide | Intentional self-harm | Requires evidence of intent |
| Homicide | Actions of another person | Legal (not necessarily criminal) determination |
| Undetermined | Insufficient evidence | Used when manner cannot be determined |

## Cause and Mechanism of Death

### Definitions

The **cause of death** is the disease, injury, or condition that initiates the lethal chain of events (for example, gunshot wound of the chest). The **mechanism of death** is the pathophysiologic process by which the cause leads to death (for example, exsanguination). The **manner of death** describes the circumstances surrounding the death. The death certificate records cause of death in a **sequential chain**: Part I lists the immediate cause and the chain of underlying causes, while Part II lists contributing conditions.

## Wound Interpretation

### Blunt Force Injuries

An **abrasion** is scraping of the epidermis, and patterned abrasions may reproduce the injury instrument. A **contusion (bruise)** is hemorrhage into soft tissue from blunt force without skin disruption; age estimation by color is unreliable. A **laceration** is tearing of tissue by blunt force, characterized by irregular edges, tissue bridges, and intact deep structures, which distinguishes it from an incision. Patterned injuries may match specific objects such as belt buckles, tire treads, or knuckle marks.

### Sharp Force Injuries

An **incised wound (cut)** is longer than deep with clean, sharp edges and no tissue bridging. A **stab wound** is deeper than long with an internal wound track. A **chop wound** is produced by a heavy edged instrument (machete or axe) and has features of both sharp and blunt force. Documentation should include dimensions, depth, direction, and anatomic structures involved.

### Gunshot Wounds

An **entrance wound** is a round or oval defect with an abrasion collar (marginal abrasion) and may show soot, stippling, or muzzle imprint depending on range. An **exit wound** is typically irregular and larger, without an abrasion collar, and may be slit-like or stellate. **Range of fire** is classified as contact (soot in wound, muzzle imprint), near-contact, intermediate (stippling/tattooing), or distant (no powder residue). The projectile trajectory is documented by wound track dissection.

![Comparison of entrance and exit gunshot wounds showing characteristic features](images/gunshot-wound-comparison.jpg)

### Asphyxia

**Ligature strangulation** produces a furrow mark on the neck corresponding to the ligature, which may be horizontal (hanging) or oblique/circumferential. **Manual strangulation** leaves contusions and abrasions on the neck, with hyoid bone and thyroid cartilage fractures especially in adults over 40. **Suffocation** includes smothering, choking, and positional asphyxia, often with minimal external findings. **Drowning** is a diagnosis of exclusion with non-specific autopsy findings (hyperinflated lungs, fluid in airways); diatom analysis is rarely helpful. **Petechiae** on the conjunctivae, face, and viscera are associated with increased venous pressure in asphyxia but are not specific.

## Decomposition and Postmortem Changes

### Early Postmortem Changes

**Algor mortis** is cooling of the body at a rate dependent on environmental temperature, body mass, and clothing. **Livor mortis** is gravitational settling of blood appearing 1-2 hours post-mortem and becoming fixed at 8-12 hours. **Rigor mortis** is stiffening from ATP depletion, beginning at 2-4 hours, fully developed at 6-12 hours, and resolving at 24-48 hours. These changes provide **estimated** postmortem intervals, with significant variability based on environmental conditions.

### Late Postmortem Changes

**Decomposition** involves autolysis and putrefaction, producing green discoloration, bloating, skin slippage, and marbling. **Adipocere** is saponification of body fat in moist environments. **Mummification** is desiccation in dry, warm environments. **Skeletonization** is complete soft tissue loss with a highly variable timeline ranging from weeks to years. Forensic entomology and other methods may assist with postmortem interval estimation.

## Special Topics

### Child Abuse

**Non-accidental trauma** is suggested by patterned injuries, injuries inconsistent with developmental age, and multiple injuries of different ages. **Abusive head trauma** presents with subdural hemorrhage, retinal hemorrhages, and encephalopathy. On skeletal survey, corner (metaphyseal) fractures and posterior rib fractures are highly suspicious. The pathologist must document findings meticulously and report to appropriate authorities.

### Toxicology

**Postmortem toxicology** specimens include blood (peripheral preferred over cardiac), urine, vitreous humor, gastric contents, liver, and hair. Postmortem redistribution can alter drug concentrations after death due to diffusion from organs. **Vitreous humor** is useful for glucose, electrolytes, and drugs because it is less subject to redistribution. Chain of custody must be maintained for all specimens.

![Forensic autopsy dissection showing wound track documentation with measurement rulers](images/forensic-wound-documentation.jpg)

### Thermal Injuries

**Burns** are classified by degree, and the pugilistic posture is a heat artifact rather than evidence of antemortem activity. **Hypothermia** may produce Wischnewski spots (gastric hemorrhagic erosions) and paradoxical undressing. In fire deaths, the pathologist must determine whether the victim was alive before the fire by looking for soot in the airways and elevated carboxyhemoglobin.

## The Forensic Autopsy Report

The report includes a complete external and internal examination with detailed documentation. **Photography** of all injuries is taken with and without scales. Diagrams and body maps document wound locations. Chain of custody documentation is maintained for all specimens. The **cause of death** and **manner of death** are stated clearly. Reports may be subpoenaed, so language must be precise, objective, and defensible.

![Body diagram showing wound mapping with measurements for medicolegal documentation](images/forensic-body-diagram.jpg)

## Clinical Pearls

Anatomic pathologists must recognize deaths requiring medicolegal investigation and promptly notify the medical examiner or coroner before performing a hospital autopsy. Distinguishing lacerations (blunt force, irregular edges, tissue bridges) from incised wounds (sharp force, clean edges) has critical medicolegal implications. Postmortem changes provide only rough estimates of time of death, as no single method is precise and environmental factors introduce significant variability. Meticulous photographic and written documentation of injuries is essential in any death with potential medicolegal significance.

## References

1. DiMaio VJ, DiMaio D. *Forensic Pathology*. 2nd ed. CRC Press; 2001.
2. Dolinak D, Matshes E, Lew E. *Forensic Pathology: Principles and Practice*. Academic Press; 2005.
3. Spitz WU, Spitz DJ. *Spitz and Fisher's Medicolegal Investigation of Death*. 5th ed. Charles C Thomas; 2020.
4. National Association of Medical Examiners. *NAME Forensic Autopsy Standards*. 2021.