Forensic Science on Post-Mortem Changes

Hypostasis

• Reddish-purple discoloration of the skin caused by blood pooling in the lower body parts due to gravity after death.
• Occurs in the superficial layers of the dermis.
• Starts as small patches (1-2 cm) within the first hour.
• Patches increase and merge into larger areas within 3-4 hours.
• Usually fully developed within 4 hours and complete in 5-6 hours.
• Becomes fixed after 8-12 hours and persists until the body begins to decompose.
• Present in all internal organs in the dependent parts of the body.

Irreversible Cessation of Respiration

• Can be assessed visually through inspection.
• Can be detected by feeling the chest for movement.
• Can be confirmed through listening for breath sounds with an instrument.
• Other tests may be used to confirm the lack of respiration.

Irreversible Cessation of Circulation

• Checked by palpating different arteries for a pulse.
• Can be confirmed through listening for heart sounds using an instrument.
• Measured by an electrocardiogram (ECG), which detects electrical activity of the heart.

Estimation of Time Since Death

• Temperature Plateau: Body temperature remains relatively stable for a period.
• Rigor Mortis: Stiffening of the muscles.
• Algor Mortis: Cooling of the body.
• Livor Mortis: Pooling of blood in lower body parts.
• Decomposition: Breakdown of the body.
• The rate of these changes can be used to estimate the time since death.

Eye Changes

• Loss of corneal and pupillary reflexes.
• Changes in pupil size.
• Opacity of the cornea.
• Appearance of the "taches noires" – dark patches on the sclera.
• Loss of intraocular pressure (drops from 10-22 mmHg during life to zero within 4-8 hours).
• Changes in the retina.
• Changes in potassium levels in the vitreous humor.

Cooling (Algor Mortis)

• First noticeable sign of death, followed by rigor mortis.
• Body temperature gradually decreases and eventually reaches the ambient temperature.
• Surface of the body cools faster than the internal core.
• Caused by cessation of energy production and failure of the body's heat-regulating center.
• Heat loss occurs through conduction, radiation, and evaporation.
• Average rate of temperature drop: 0.4-0.7°C/h.
• Body reaches environmental temperature in 16-20 hours.

Factors Affecting Algor Mortis

• Environmental temperature.
• Air movement (wind).
• Humidity.
• Medium in which the body is found (e.g., water, soil).
• Body composition (e.g., age, sex, build).
• Clothing or coverings.
• Body position and posture.
• Cause of death.

Postmortem Changes of Forensic Importance

• Hypostasis: As described above.
• Rigor Mortis: Stiffening of muscles after death, progresses through stages.
• Putrefaction: Decomposition of the body, characterized by bloating, discoloration, and odor.

This quiz explores key concepts in forensic science related to post-mortem changes, specifically hypostasis and cessation of vital functions. Understand how blood pooling affects skin coloration and learn the methods used to confirm the absence of respiration and circulation. Test your knowledge on these critical aspects of forensic evaluation.