Forensic Medicine · Medico-Legal Autopsy and Postmortem Changes (Thanatology)

Casper's dictum compares the rate of decomposition of a body in different environments. What is the correct ratio it describes?

  • A 1 week in air = 2 weeks in water = 8 weeks in soil
  • B 1 week in water = 2 weeks in air = 8 weeks in soil
  • C 1 week in soil = 2 weeks in water = 8 weeks in air
  • D 1 week in air = 4 weeks in water = 16 weeks in soil
Correct answer: A. 1 week in air = 2 weeks in water = 8 weeks in soil

Explanation

Casper's dictum states: "One week in open air = two weeks submerged in water = eight weeks buried in earth." This reflects the effect of oxygen availability, temperature, insect access, and moisture on decomposition rate. Air decomposition is fastest because insects, aerobic bacteria, and evaporation all operate maximally. Submersion slows insect access and reduces oxygen. Burial further retards decay through soil insulation, anaerobic conditions, and reduced temperature. This dictum is foundational for estimating postmortem interval from contextual circumstances.

Reference: The Essentials of Forensic Medicine and Toxicology (Narayan Reddy), 34th ed.

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