Early Post-Mortem Changes

Introduction

• Focus on early post-mortem changes after death.
• Key concepts: Algor mortis, Rigor mortis, and Liver mortis.

Algor Mortis (Post-Mortem Cooling)

• Definition: The cooling of the body after death.
• Initial Phase: No immediate drop in temperature due to endogenous heat production from living tissues.
• Phases of Temperature Decline:
  1. Plateau Phase (0-1 hour): No temperature decrease due to metabolic processes.
  2. Linear Phase (1-12 hours): Temperature falls 0.4 to 0.6 °C per hour.
  3. Terminal Phase (after 16 hours): Body temperature stabilizes above baseline due to bacterial activity.
• Measurement Sites: Core temperature can be measured from the rectum or subhepatic space.
• Conditions Delaying Decline:
  • Heat stroke, tetanus, and poisoning (excessive muscle contraction leading to heat).

Liver Mortis (Postmortem Staining)

• Definition: Bluish-purple discoloration due to blood pooling in dependent areas of the body.
• Contact Pallor: Areas compressed against a surface do not stain and appear pale.
• Stages:
  • Initiation (0-30 minutes): Staining begins in dependent areas.
  • Confluent Staining (4 hours): Large stained areas appear.
  • Fixation (6-8 hours): Staining fixed; position of the body at the time of death can be identified.
• Secondary Lividity: Occurs if body position changes before fixation.
• Absence of Liver Mortis: In cases like drowning (continuous movement) or severe blood loss.
• Color Variations: Different causes of death influence staining color (e.g., cherry red for carbon monoxide poisoning).

Rigor Mortis (Cadaveric Rigidity)

• Definition: Stiffening of the muscles after death.
• Difference from Cadaveric Spasm: Cadaveric spasm occurs immediately after death; rigor mortis develops after a delay.
• Process:
  • Initial Primary Flaccidity: Muscles relaxed immediately after death.
  • Onset of Rigor Mortis: Starts 1-2 hours after death, peaks at 6 hours, then leads to secondary flaccidity.
• Mechanism: Calcium leakage into muscle cells leads to prolonged contraction due to lack of ATP after death.
• Nishtan Rule: Sequence of rigor mortis onset begins in involuntary muscles (heart) and progresses through the body.
  • Eyelids → Neck → Lower jaw → Face → Chest/Upper limbs → Abdomen → Lower limbs → Distal extremities.
• Duration:
  • Cooler temperatures prolong rigor mortis (24-48 hours in winter; 18-36 hours in summer).

Summary of Changes

1. Algor Mortis: Helps estimate time of death.
2. Liver Mortis: Indicates body position at time of death.
3. Rigor Mortis: Aids in determining time of death and muscle rigidity progression.

Conclusion

• Understanding these processes is essential for forensic investigation.
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