Early Post-Mortem Changes

Introduction

• Overview of early post-mortem changes after death: Algor mortis, Rigor mortis, and Liver mortis.
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Algor Mortis (Post-Mortem Cooling)

• Definition: Cooling of the body after death.
• Phases of Algor Mortis:
  1. Initial Phase (Plateau Phase):
     • No temperature decrease for the first hour due to endogenous heat production from living tissues.
  2. Linear Decrease:
     • Body temperature starts to fall after one hour.
     • Typical rate of temperature decrease: 0.4 to 0.6°C per hour (lasts for 12 to 16 hours).
  3. Terminal Phase (Plateau):
     • After 16 hours, temperature stabilizes above baseline due to bacterial activity.
     • Sigmoid/inverted S-shaped curve illustrates the temperature decline.
• Conditions Delaying Temperature Decline:
  • Heat stroke: Temperature decrease may start after 2 hours.
  • Tetanus and strychnine poisoning: Excess muscle contraction produces heat.
  • Septicemia: Elevated body temperature at the time of death.

Liver Mortis (Post-Mortem Staining)

• Also known as lividity or hypostasis.
• Definition: Bluish-purple discoloration due to blood pooling in dependent body parts after death.
• Contact Pallor: Areas in contact with a surface do not show staining.
• Stages of Liver Mortis:
  1. Initial Staining: Begins within 30 minutes.
  2. Confluent Staining: Observable by 4 hours.
  3. Fixation: Occurs around 6-8 hours; staining pattern remains unchanged even if body position is altered.
• Secondary Lividity:
  • Occurs if body position is changed before fixation.
• Conditions Affecting Liver Mortis:
  • Absence: Drowning (constant position change) or severe blood loss.
  • Special Patterns:
    • Glove and stocking pattern in hanging due to gravity.
  • Color Variations Due to Poisoning:
    • Carbon monoxide: Cherry red.
    • Cyanide: Brick red.
    • Nitrites: Reddish-brown.
    • Hypothermia: Bright pink.

Rigor Mortis (Cadaveric Rigidity)

• Definition: Stiffening of muscles post-death.
• Comparison with Cadaveric Spasm:
  • Cadaveric spasm occurs immediately after death and cannot be altered; can provide clues about cause of death.
• Phases of Rigor Mortis:
  1. Primary Flaccidity: Muscles relaxed immediately after death.
  2. Onset of Rigor Mortis: Begins 1-2 hours after death, peaks when ATP levels are 15% of normal.
  3. Secondary Flaccidity: Muscles relax after rigor mortis has passed.
• Mechanism:
  • Calcium leaks from sarcoplasmic reticulum causing sustained contraction due to lack of ATP.
• Nishtan Rule:
  • Sequence of rigor mortis onset:
    1. Involuntary muscles (heart).
    2. Eyelids, neck, lower jaw, face, chest, upper limbs, abdomen, lower limbs, fingers and toes.
• Duration:
  • Longer in cooler climates (24-48 hours in winter vs. 18-36 hours in summer).

Summary of Post-Mortem Changes

• Algor Mortis: Indicator of time since death; initial plateau phase, falls at 0.4-0.6°C/hr.
• Liver Mortis: Helps determine position at time of death; onset in 30 min, fixation in 6-8 hours.
• Rigor Mortis: Indicates time since death; sequence and duration vary by climate.

Conclusion

• Recap of the importance of understanding these changes in forensic contexts.
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