Forensic Science: Postmortem Changes Quiz

Forensic Medicine

• Forensic pathology is a branch of medicine applying medical principles and knowledge to legal problems.
• It bridges the gap between medicine and law by applying medical knowledge to legal issues.

Types of Autopsy

• A clinical or academic autopsy is performed with the consent of relatives to determine the extent of disease that led to death.
• A medico-legal or forensic autopsy is performed by legal authority to investigate sudden, suspicious, obscure, unnatural, litigious, or criminal deaths.

Objectives of Forensic Autopsy

• Positive identification of the body, assessing body size, physique, and nourishment.
• Determining the cause of death, or in newborns, whether live birth occurred.
• Determining the mechanism and time of death, if necessary.
• Demonstrating all external and internal abnormalities, malformations, and diseases.
• Detecting, describing, and measuring external and internal injuries.
• Obtaining samples for analysis, including microbiological and histological examinations.
• Retaining relevant organs and tissues as evidence.
• Obtaining photographs and videos for evidentiary and teaching purposes.
• Providing a full written report of the autopsy findings.
• Offering expert interpretation of the findings.
• Restoring the body to the best possible cosmetic condition before release.

Thanatology (Death & Postmortem Changes)

Death and Postmortem Changes

• Somatic (clinical death) is the permanent cessation of the integrated functioning of an individual, associated with the irreversible loss of circulation, respiration, and central nervous system innervations.
• Molecular (cellular death) is the death of individual organs and tissues; cortical neurons die after 3-7 minutes, while skin and bone remain alive for several hours.
• Medico-legal importance: organs transplantation occurs during the period of molecular life.

Cause, Mechanism, and Manner of Death

• Cause of death is any injury or disease producing physiological derangement leading to death (e.g., hemorrhage, septicemia, cardiac arrhythmia, cardiopulmonary arrest).
• Mechanism of death is the physiological derangement produced by the cause of death.
• Manner of death describes how the cause of death occurred (e.g., accidental, homicidal, suicidal, natural, unidentified).

Diagnosis of Somatic (Clinical) Death

• Cessation of Circulation:

  • Loss of pulsations in major arteries (carotid and femoral).
  • Absence of perceptible blood pressure.
  • Loss of heartbeats (for 5 minutes).
  • Flatline on all ECG leads (for 5 minutes).

• Cessation of Respiration:

  • Apnea (checked by careful auscultation).
  • Severe hypoxia and hypercapnea (revealed by arterial blood gas analysis).

• Cessation of Brain Function (brain death):

  • Unresponsiveness to any stimulus (deep coma).
  • Absence of motor responses (no response to painful stimuli).
  • Absence of reflex responses indicative of continued brain stem function (absence of corneal reflex, absence of pupillary response to bright light).
  • Absence of spontaneous eye movements or those in response to head turning (oculocephalic response).
  • Absence of eye movement in response to ice water irrigation of the ear (oculovestibular response).
  • Absence of gag reflex to a catheter placed in the larynx and trachea.
  • Apnea (arterial PCO2 level exceeding 50 mm Hg).

• Persistent Vegetative State (PVS): A patient loses higher-level brain function but retains brainstem functions (respiration and circulation) (e.g., massive cerebral infarcts, hypoxic encephalopathy, head trauma)

Postmortem (PM) Changes

• PM Cooling (Algor Mortis):

  • Stoppage of heat production due to cessation of oxidative processes and metabolism.
  • Heat loss through conduction, convection, and radiation.
  • Body temperature decreases by 1-1.5°C per hour.

• Factors affecting the rate of cooling:

  • Age (infants cool rapidly due to large surface area).
  • Sex (females cool more slowly due to subcutaneous fat).
  • Obesity (subcutaneous fat is a poor heat conductor).
  • Environment (bodies in well-ventilated rooms cool faster than those in closed rooms; bodies in water cool twice as fast as bodies in air); (clothed bodies cool more slowly than naked bodies).

• Primary Flaccidity (Contact Flattening):

  • Complete muscle relaxation and loss of reflexes at death.
  • Face assumes peaceful expression; jaw drops; pupils dilate.
  • Muscle contraction due to electrical stimuli is absent.
  • Convex muscle parts flatten against flat surfaces.

• Change of the Eyes:

  • Loss of corneal and light reflexes.
  • Retinal vessel segmentation and optic disc pallor (visible within 15 minutes).
  • Intraocular pressure drop leading to sunken and flaccid eyeballs (visible within 30 mins).
  • Cloudy and opaque cornea (visible after 2 hours).
  • Brownish discoloration (tache noire) of exposed sclera (visible within 3-4 hours), due to accumulation of cellular debris and dust.

• Changes of the Skin: skin becomes pale and opaque due to absent circulation. Skin loses elasticity, so wounds do not gap.

• PM Lividity (Hypostasis or Livor Mortis):

  • Bluish discoloration and staining of the dependent parts of the body due to gravitational fluid blood and stagnation in capillaries and veins.
  • Starts immediately after death due to cessation of circulation.
  • Appears within one hour after death.
  • Maximum and fixed in approximately 8 hours.
  • Does not alter with body position changes.
  • Colour (light blue to deep blue, red or brown): can vary based on cause of death.

• MLI of Livor Mortis: (colour; extent ; site ) - It is a sure sign of death.

• It denotes the time that has passed since death, starting to appear after 1 hour, and reaching maximum after 8 hours.

• Its site indicates the position of the body during the first 8 hours after death.

• PM Rigidity (Rigor Mortis):

  • Progressive rigidity of voluntary and involuntary muscles following primary flaccidity and preceding secondary flaccidity.
  • Full rigor mortis within 12 hours after death.
  • Mechanism: depletion of ATP in muscle cells, leading to actin and myosin filament bonding.
  • MLI of Rigor Mortis: is a sure sign of death. It denotes the time passed since death by its start, extent, and disappearance rate(starts in face and progresses downward).
  • Factors that affect rigor mortis: temperature, cause of death, muscle mass, body weight.
  • Differentiation from cold or heat stiffening or cadaveric spasm.

• Secondary Flaccidity:

  • Muscles become soft and flaccid after rigor mortis.
  • Do not respond to mechanical or electrical stimuli.
  • Autolysis of tissue proteins leads to this stage.

• Putrefaction (PM Decomposition):

  • Final stage of decomposition of soft tissues, leaving only bones.
  • Mechanism:
    • Autolysis: release of enzymes from tissue cells, leading to softening and liquefaction.
    • Bacteria: aerobic and anaerobic bacteria break down tissues, produce gases, and cause various changes.
  • MLI of Putrefaction: A sure sign of death

• Effect of Putrefactive Gases:

  • Expulsion of fetus from gravid uterus.
  • Flotation of drowned bodies.
  • Expulsion of feces and gastric contents.
  • Protrusion of tongue and eyes with froth on mouth and nose.

• Factors affecting Putrefaction

  • Temperature
  • Air
  • Moisture
  • Age
  • Cause of death.

• Conditions Replacing Putrefaction

  • Maceration: intrauterine fetal death (aseptic autolysis), temporary state.
  • Adipocere: in water or wet ground, greasy yellowish-grey wax-like material, caused by bacterial anaerobic oxidation of fats.
  • Mummification: in desert climates (no water) dry condition (slow or stopped putrefaction), dehydrated body.

• Skeletalization (Skeletonization): Final decomposition stage where only bones remain.

Test your knowledge on key concepts of postmortem changes, including maceration in fetuses, adipocere formation, mummification, and the preservation of injury. This quiz will challenge your understanding of the processes that occur after death and their implications in forensic science. Perfect for students and professionals interested in forensic pathology.