Time Since Death Estimator

How the time since death estimator works

After death the body loses heat to its surroundings. That loss is not linear: there is an initial plateau of one to three hours while the core temperature holds, then a steep sigmoid fall, then a slow approach to ambient. Henssge's model captures this with a double exponential of the standardised temperature Q.

The corrective factor matters as much as the temperature reading. Clothing, bedding, still or moving air, and immersion all change the rate of loss, so the model works on a corrected body mass rather than raw weight. This calculator solves the equation numerically for t and reports the published confidence band, which widens as the body approaches ambient.

Frequently asked questions

How is time since death estimated from body temperature?

The standardised temperature Q is calculated from rectal, ambient, and normal body temperature, then Henssge's double-exponential cooling equation is solved for elapsed time. The cooling constant depends on body mass corrected for clothing and surroundings.

How accurate is the Henssge method?

Under favourable conditions the published 95% confidence band is roughly plus or minus 2.8 hours, widening to 4.5 hours or more once the body nears ambient temperature. It is a range, never a single time.

What invalidates a body cooling estimate?

Fever or hypothermia at death, a moved body, direct sunlight, heating or air conditioning, immersion, and a changing ambient temperature. Each breaks the model's assumption of one steady cooling environment.

Why is rectal temperature used?

It approximates the deep core temperature and is far less affected by surface conditions than skin. Measurement depth and technique must be consistent, since a shallow reading reads low.

What other methods estimate the post-mortem interval?

Rigor mortis, livor mortis, potassium levels in vitreous humour, stomach contents, decomposition staging, and forensic entomology. Cooling is most useful in the first day; the others take over after that.

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