## Algor Mortis: Cooling Rate and Variables **Key Point:** Algor mortis (post-mortem body cooling) follows a predictable but variable rate that is influenced by multiple environmental and individual factors. ### Rate of Algor Mortis **High-Yield:** The body cools at approximately **1–1.5°F (0.5–0.8°C) per hour** in the first 12 hours under standard ambient conditions (around 70°F / 21°C). ### Factors Affecting Cooling Rate | Factor | Effect on Cooling | |--------|-------------------| | **Ambient temperature** | Lower ambient = faster cooling | | **Body composition** | Lean body cools faster; obese body cools slower (due to insulation) | | **Clothing/covering** | Insulation slows cooling | | **Air circulation** | Wind/drafts accelerate cooling | | **Body surface area** | Larger surface area = faster cooling | | **Cause of death** | Fever, sepsis, or hyperthermia at death = slower initial cooling | | **Immersion** | Water immersion accelerates cooling (3–4× faster) | **Clinical Pearl:** The "Henssge nomogram" is used in forensic pathology to estimate time of death by correcting for ambient temperature and body weight, accounting for the variable nature of algor mortis. ### Why Constant Rate is Incorrect **Warning:** Algor mortis does NOT follow a perfectly linear rate. The cooling curve is biphasic: - **Rapid phase (0–12 hours):** ~1–1.5°F/hour - **Slow phase (>12 hours):** Approaches ambient temperature asymptotically (cooling slows as body temperature nears environment) This is why time-of-death estimates using algor mortis alone are unreliable after 12 hours.
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