Postmortem Changes

Immediate & Eye Changes - First Signs Off

• Immediate Signs:
  • Cessation of vital functions: Respiration, Circulation, Brain activity.
  • Primary flaccidity: Initial total muscle relaxation.
  • Pallor mortis: Paleness of the skin.
• Eye Changes:
  • Loss of corneal reflex (no blink).
  • Corneal opacification/clouding (develops in first few hours).
  • Tache Noire Sclerotique: Brownish-black triangular discoloration on sclera if eyes open; appears 6-12 hrs.

    ⭐ Tache Noire Sclerotique is a brownish-black triangular discoloration appearing on the sclera if eyelids remain open after death.

  • Intraocular pressure ↓ (Kevorkian sign).
  • Retinal vessel segmentation ("cattle trucking" on fundoscopy).

Algor Mortis - Body's Big Chill

• Definition: Postmortem body cooling.
• Mechanism: No metabolic heat; heat loss to environment. Follows Newton's Law of Cooling (sigmoid).
• Rate: Avg. 0.8-1.0°C/hr (first 6 hrs), then 0.4-0.5°C/hr; varies.
• Formula (Conceptual): $T_{body} - T_{ambient} = (T_{initial} - T_{ambient}) e^{-kt}$
• Rule of Thumb (Approx.): (Normal Body Temp - Rectal Temp) / 1.5 = Hours since death
• Factors Affecting:
  • Body: Build, surface area, clothing.
  • Environment: Temp, humidity, air, water.
• Medico-legal: Estimates Time Since Death (TSD); best in first 12-18 hrs.

⭐ Most accurate temperature: rectal or liver.

Livor Mortis - Pooling Hues Clues

• Definition: Postmortem staining (lividity) from gravitational blood settling in dependent parts.
• Timeline:
  • Appears: 1-2 hrs postmortem.
  • Developed: 4-6 hrs.
  • Fixed: 8-12 hrs (coagulation, vessel permeability changes).
• Distribution: Dependent areas; absent at pressure points. Tardieu spots (petechiae).
• Color Clues & Significance:

  Color	Cause
  Cherry-red	CO poisoning, cyanide, cold 📌
  Dark blue/purple	Asphyxia
  Bronze	Clostridium perfringens
  Brown	Methaemoglobinaemia

• Medico-legal: TSD estimation, body position, indicates if moved after fixation.

⭐ Livor mortis blanching on pressure means not fixed; no blanching indicates fixation (death ≥ 8-12 hours prior).

Rigor Mortis - The Stiff Truth

• Definition: Postmortem stiffening of all body muscles.
• Mechanism: $ATP$ depletion $\rightarrow$ irreversible actin-myosin complexes.
• Sequence (Nysten's Law): Progressive stiffening.

• Factors affecting:
  • Temperature: Faster in ↑ heat, slower in ↓ cold.
  • Pre-death muscular activity: Faster if ↑ active.
  • Age/Physique: Varies onset/intensity.
• Conditions simulating/modifying: Cadaveric spasm (instantaneous), heat stiffening, cold stiffening.
• Medico-legal importance: Estimates Time Since Death (TSD), indicates body position at death, possible struggle.

⭐ Cadaveric spasm: instantaneous rigor, often in violent/drowning deaths, maintains death position.

Decomposition - Nature's Cleanup Crew

• Autolysis: Aseptic, enzymatic self-digestion.
• Putrefaction: Bacterial action.

⭐ Marbling is caused by the reaction of hydrogen sulfide (from bacteria) with hemoglobin in superficial veins, forming sulfmethemoglobin.

• Other Forms of Decomposition:

  • Mummification: Dry, arid conditions. Skin dry, leathery; organs shrunken.
  • Adipocere (Saponification): Moist, anaerobic environment. Fats → waxy, soap-like substance (weeks-months).
  • Skeletonization: Final stage; soft tissues gone.

• Casper's Dictum: Decomposition rate: 1 wk (air) = 2 wks (water) = 8 wks (buried).

• Forensic Entomology: Insect activity (maggots) estimates TSD & body relocation.

High‑Yield Points - ⚡ Biggest Takeaways

• Algor Mortis: Body cooling, ~1-1.5°C/hr initially.
• Livor Mortis: Starts 30 min-2 hrs, fixes 8-12 hrs; differentiates from contusions.
• Rigor Mortis: Begins 1-2 hrs (face/jaw), complete by 12 hrs, lasts 24-36 hrs; Nysten's Law.
• Putrefaction: Greenish RIF discoloration at 24-36 hrs; marbling follows.
• Adipocere: Saponification in moist, anaerobic conditions; takes weeks to months.
• Mummification: Occurs in dry, arid environments; preserves tissues.
• Tache Noire: Scleral drying artifact if eyes open_