Forensic autopsy and thanatology

The study of autopsy and thanatology techniques provides a systematic framework for determining the cause and manner of death through the biological and procedural evaluation of a deceased body. Autopsies are categorized into medicolegal investigations, which require state authorization for unnatural deaths, and pathological examinations, which require familial consent to investigate natural disease processes. Specialized autopsy techniques (e.g., virtual autopsy) further refine the diagnostic process in complex cases. The procedural execution of an autopsy follows specific sequences and utilizes standardized incisions and organ removal techniques. Forensic disinterment, or exhumation, and the preservation of specific viscera using specialized preservatives are essential components of the medicolegal investigation in cases of suspected poisoning or buried remains. Thanatology tracks the transition from somatic to molecular death, identifying critical markers during the supravital period and the postmortem phase.

See "Types of autopsy" in "Death" for more details on forensic autopsy and differences between a forensic autopsy and a clinical autopsy.

Specialized autopsy types

• Psychological autopsy
  • A retrospective assessment of the deceased's mental state prior to death
  • It involves interviewing family members and reviewing medical records to determine the manner of death, particularly in cases where suicide is suspected.
• Virtual autopsy
  • The use of advanced medical imaging (e.g., CT or MRI) to perform a non-invasive postmortem examination
  • It is used to document injuries, locate foreign bodies (e.g., bullets), and reconstruct trauma without traditional dissection.

Autopsy technique

Sequence

The order of cavity dissection is modified based on the suspected cause of death to avoid the creation of artifacts or the loss of volatile evidence.

Types of incisions

Incisions are chosen based on the need for specific exposure and, in some cases, cosmetic considerations.

• I-shaped incision
  • The most common and simplest incision
  • It extends from the chin in the midline down to the pubic symphysis.
• Y-shaped incision
  • Primarily used in females for cosmetic purposes
  • The incision begins at both acromion processes, meets at the xiphoid process, and extends down to the pubic symphysis.
• Modified Y-shaped incision
  • Used when a detailed examination of the neck is required (e.g., in cases of strangulation or hanging)
  • It begins behind the ears at the mastoid processes and extends down the sides of the neck to meet at the suprasternal notch.

Organ removal

Techniques of organ removal

The choice of technique depends on the suspected cause of death, the presence of infectious diseases, and the need to study inter-organ relationships.

Organ-specific dissection techniques

Specific procedures are utilized for the examination of individual organs and systems to ensure no injuries or pathological findings are overlooked.

• Scalp: dissected using a bimastoid incision to expose the skull vault
• Skull vault
  • Adults: removed using a Stryker saw
  • Fetus/newborns: removed using scissors
  • Barr’s technique: the most common method in infants, involving 4 flaps
  • Beneke’s technique: involves 2 flaps
• Brain
  • Routinely performed as a fresh dissection
  • Formalin fixation is considered ideal for detailed neurological examination
• Spinal cord
  • Not routinely dissected
  • It is performed in cases of strychnine poisoning or whiplash injury, typically using a posterior approach.
• Heart: dissected using the inflow-outflow method (RA → RV → LA → LV) to evaluate valves and chambers
• Stomach
  • Ligation: The cardiac and pyloric ends are double-ligated and cut in between to preserve contents for chemical analysis.
  • Incision: typically opened along the greater curvature.
  • Magenstrasse (lesser curvature): evaluated specifically in cases of acid consumption, as this area often shows the maximum damage.

Preservation of viscera for chemical analysis

The preservation of internal organs is essential for toxicological analysis to detect the presence of poisons or drugs. In certain legal contexts, a body may be disinterred for forensic investigation through the process of exhumation.

Standard forensic protocols mandate the collection and preservation of specific biological samples to ensure the accuracy of laboratory results.

• Routine samples
  • Blood: typically collected from a peripheral vein; it is considered the most reliable sample for quantitative analysis.
  • Stomach and contents: preserved to detect the presence of unabsorbed poisons
  • Liver and kidney: primary organs for detecting metabolized substances and heavy metals
• DNA identification samples
  • Blood: preserved with EDTA
  • Teeth: The dental pulp is the preferred source for DNA in decomposed or charred remains.
  • Other: deep muscle tissue and bone (e.g., femur)

Preservatives

Biological samples must be stored in appropriate preservatives to prevent chemical degradation or bacterial contamination.

Exhumation

Exhumation is the lawful digging out of a buried body for forensic examination.

• Authorization: must be authorized by a competent legal authority (e.g., a court, coroner, or magistrate)
• Procedure
  • Identification: The grave and the remains must be definitively identified by family or legal records.
  • Soil Samples: Forensic protocols require the collection of soil samples from above, below, and adjacent to the body. This is necessary to differentiate between poisons ingested by the deceased and those that may have entered the body from the surrounding environment (postmortem imbibition), such as arsenic.

Classification of autopsy findings

In cases where a standard examination does not provide an immediate or definitive cause of death, findings are classified into specific forensic categories.

• Obscure autopsy
  • An autopsy where the initial gross (visual) findings are insignificant or misleading.
  • The cause of death is determined only after additional specialized tests, such as toxicology or histopathology.
• Negative autopsy
  • An autopsy in which no definitive cause of death is found, even after exhaustive macroscopic, microscopic, and toxicological examinations.
  • This occurs in approximately 5% of all forensic autopsies.
• Medical malpractice autopsy: specifically focused on investigating deaths suspected of resulting from a negligent or substandard medical act

Thanatology is the study of death, encompassing the biological, social, and legal aspects of the cessation of life. Taphonomy refers specifically to the study of the postmortem resorption and decomposition of the body.

The postmortem period is divided into the supravital period, early postmortem changes, and late postmortem changes (decomposition).

Supravital period

The supravital period represents the interval between clinical death and molecular death.

• Clinical significance: This window is critical for organ harvesting for transplantation; for example, the cornea must be harvested within 6 hours.
• Supravital reactions: see "Supravital reactions" in "Death".

Early postmortem changes

These changes occur within the first 24 hours and are the primary markers used to estimate the time since death (TSD).

• Eye changes
  • Kevorkian sign (cattle trucking): fragmentation of retinal vessels occurring within minutes to 1 hour postmortem.
  • Tache noire sclerotica: triangular brown opacities on the sclera due to drying (3–6 hours).
• Algor mortis (postmortem cooling)
  • The fall in body core temperature (BCT) follows a sigmoid (inverted S) curve.
  • BCT is measured via a thanatometer in the rectum, subhepatic space, or ear.
  • Postmortem caloricity
    • A condition where the body remains warm, or the temperature rises after death.
    • Causes include heat stroke, tetanus, and septicemia.
• Rigor mortis
  • Usually occurs within 1–2 hours of death
  • Starts to reside after about 24 hours
  • Follows Nysten rule, progressing from the head (eyelids, jaw) downward to the thorax and lower limbs.
  • Cadaveric spasm
    • Rigidity that occurs at the moment of death without primary flaccidity.
    • It is always an antemortem phenomenon (e.g., seen in drowning or suicidal gunshots).
• Livor mortis
  • Definition: purple-red discoloration of dependent areas of skin not exposed to pressure that begins 20–30 minutes after circulation stops due to blood settling under the force of gravity (hypostasis)
  • Onset: 30 minutes to 2 hours after death
  • Maximum observed at 6–12 hours, after which blanching is no longer possible.
  • Postmortem staining colors: The color of livor mortis can be diagnostic for specific poisons or conditions.

Late postmortem changes

See "Late postmortem changes" in "Death"

Putrefaction

Putrefaction is the final stage of decomposition and encompasses four key dimensions: color changes, secondary relaxation, gas production, and tissue liquefaction.

• Color changes
  • First external sign: greenish discoloration of the skin over the flanks
  • Onset within 12–48 hours of death and may vary with environmental temperature
  • Marbling: 36–48 hours after death
• Secondary relaxation
  • Musle flacidity
  • Due to autolysis
• Gas formation
  • Bacteria produce gases (such as methane, carbon dioxide, and hydrogen) as they consume the body's carbohydrates, proteins, and lipids.
  • Results in distension over several areas of the body (e.g., abdomen, scrotum)
  • Postmortem purge: The pressure from these gases can force reddish-brown fluid out of the mouth and nose.
  • Occurs 36–48 hours after death
• Tissue liquefaction
  • The rate at which tissues liquefy follows a predictable sequence based on their tissue structure and bacterial load.
  • Earliest change: larynx and trachea
  • Early liquefaction
    • Stomach and Intestine
    • Spleen
    • Liver
    • Brain
    • Heart
  • Late liquefaction: prostate in males; non-gravid uterus in females
  • Last to decompose: bone and teeth

Factors Influencing Putrefaction

• Environment: Putrefaction is accelerated by warmth and moisture.
• Casper's rule
• Poisons: certain substances (e.g., strychnine, heavy metals, and carbolic acid) can delay the onset of putrefaction.