Estimate time since death with a simplified Henssge-based body-cooling worksheet that also shows broad postmortem-change timelines.
Estimating the time since death — the postmortem interval (PMI) — is a standard part of forensic pathology and medicolegal death investigation. One of the most commonly used early approaches is algor mortis: the cooling of the body after death. The Henssge nomogram is a reference approach that models this cooling with a double-exponential curve rather than a simple straight line.
This page implements a simplified Henssge-based worksheet using core temperature, ambient temperature, body weight, clothing, body build, and environment adjustments. It provides an educational PMI estimate with a broad uncertainty range rather than a formal forensic opinion.
The postmortem-change table is included as supporting context only. In real casework, scene information, body handling history, and other forensic findings matter alongside temperature.
PMI estimation helps organize timelines, compare witness statements, and narrow an initial review window. This worksheet is best used for forensic education and preliminary scene review rather than as a substitute for a formal medicolegal opinion.
Henssge double-exponential: Q = (T_rectal − T_ambient) / (37.2 − T_ambient) = 1.25 × e^(-kt) − 0.25 × e^(-5kt) Cooling constant k = 1.2815 / (corrective_factor) Corrective factor = clothing × mass_factor × build_adj × surface_adj Solved iteratively for time t (hours)
Result: Estimated PMI: ~8.5 hours (range 7.2–9.8 h)
Body cooling from 37.2°C to 30°C in a 20°C environment with standard correction factor ~1.0 yields a temperature ratio Q of 0.59. Solving the double-exponential equation gives approximately 8.5 hours postmortem, with a ±15% confidence interval of 7.2 to 9.8 hours.
Use consistent units, verify assumptions, and document conversion standards for repeatable outcomes.
Most mistakes come from mixed standards, rounding too early, or misread labels. Recheck final values before use.
Keep assumptions explicit and treat the result as a worksheet estimate, not a substitute for a full forensic review.
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This page uses a simplified Henssge-style body-cooling worksheet. It combines core temperature, ambient temperature, body weight, clothing, body habitus, and surface or environment adjustments to estimate a postmortem interval from cooling, then places that estimate beside standard rigor and livor timelines.
It is not a forensic report. Real postmortem interval work requires scene information, body handling history, environmental variation, and other postmortem findings in addition to temperature.
The Henssge nomogram achieves ±2.8 hours accuracy (95% CI) within the first 24 hours postmortem under standard conditions. Accuracy decreases after 24 hours as the body approaches ambient temperature. Environmental variables (wind, rain, heating) reduce accuracy further.
Rectal temperature most closely reflects core body temperature, which is the basis of the Henssge model. Brain (tympanic) or hepatic temperatures can be used but have different cooling curves. Rectal temperature is the standard in forensic practice and is the temperature the nomogram was validated with.
After death, body temperature remains relatively stable for 30-90 minutes before linear cooling begins. This "sigma phenomenon" is due to residual metabolic heat, thermal inertia, and ongoing enzymatic reactions. The double-exponential model accounts for this plateau; simple Newton's law does not.
Yes. The model assumes a starting body temperature of 37.2°C. If the person had a fever (39-40°C), the PMI will be underestimated. Similarly, hypothermia before death overestimates PMI. Adjusting the baseline temperature improves accuracy when antemortem temperature is known.
Bodies in water cool approximately twice as fast as in air at the same temperature. The water correction factor (0.5) partially accounts for this, but accuracy in aquatic environments is reduced compared to indoor scenes. Current, water temperature variability, and clothing significantly affect cooling.
Forensic pathologists use multiple modalities: rigor mortis progression (2-12 hours onset, 24-36 hours resolution), livor mortis fixation (8-12 hours), vitreous potassium concentration, gastric contents analysis, entomological evidence (insect activity), and scene investigation findings. Use this as a practical reminder before finalizing the result.