Algor mortis: cooling of the body
- Finding
After death the body loses heat until it matches the surrounding temperature, at a rate that depends on many conditions.
What it is
Algor mortis is the cooling of the body after death. Once metabolism stops, the body no longer produces heat and loses it to the surroundings by conduction, convection and radiation until it reaches ambient temperature. The core temperature curve is not a straight line: there is usually an initial plateau of variable length while the gradient between skin and core builds up, then a faster fall that gradually slows. That is why the old rule of «about one degree per hour» is an unreliable simplification. Current methods, such as the Henssge nomogram, combine rectal temperature, ambient temperature, body weight and corrective factors for clothing and environment, and even then they give a wide interval.
How to tell it apart
- Environmental hypothermia: the body may have been cold before death, which invalidates calculations that start at 37 degrees.
- Fever, heatstroke, seizures or heavy exertion before death raise the starting temperature and lengthen the apparent interval.
- Immersion in water: cooling is faster than in air at the same temperature.
- Refrigerated or moved body: changes in ambient temperature after death distort the curve.
How to recognise it
- Progressive coldness to touch, first in hands, feet and face, then in the trunk.
- Core temperature measured in the rectum (or another deep site) with a low-reading thermometer.
- Comparison with ambient temperature measured at the same place and time.
How it forms
- Without metabolism no heat is produced, and the body loses heat to its surroundings.
- The surface cools first; the core lags because tissues conduct heat poorly (the plateau).
- Cooling is faster with more surface area relative to weight (children, thin people), little clothing, air movement or immersion in water.
- Cooling is slower with obesity, clothing or bedding, a warm environment, and fever or hyperthermia before death.
Next step: what to do and document
- Measure and record core and ambient temperatures, with the exact time and site of each measurement.
- Describe clothing, bedding, the surface the body lay on, any water, wind, sun or heating, and whether the body was moved.
- Weigh or estimate the body weight and record it, because the calculation needs it.
- If measurements are repeated, use the same site and the same instrument.
- Express the result as a range and combine it with lividity and rigor.
Common mistakes
- Using the one-degree-per-hour rule as if it were an exact calculation.
- Not measuring ambient temperature at the scene, or measuring it hours later somewhere else.
- Forgetting the initial plateau: in the first hours the core temperature barely falls.
- Ignoring that the body may have been hypothermic or febrile before death.
Test yourself
Think of the answer, then tap the question to see it.
Why does rectal temperature hardly change in the first hours after death?
Because of the initial plateau: the surface cools first and the core lags until the thermal gradient is established.
What data does the Henssge nomogram use?
Rectal temperature, ambient temperature, body weight and a corrective factor for clothing, covering and environmental conditions.
How does fever before death affect a cooling-based estimate?
The starting temperature is higher, so a calculation that assumes normal temperature underestimates the time since death.
Does a body cool faster in water or in air at the same temperature?
In water, because water conducts heat better than air.
Connections
Educational content on forensic and legal medicine; not legal advice and no substitute for the technical guides of Colombia's National Institute of Legal Medicine and Forensic Sciences. Laws change: each page links the official text and says when it was last checked. For a real case, follow the guide in force and ask the competent authority.
Sources: Development of a mobile application to estimate time of death based on the compound method (Zirn A et al.) (International Journal of Legal Medicine, 2026); An assessment of the Henssge method for forensic death time estimation in the early postmortem interval (Heinrich F et al.) (International Journal of Legal Medicine, 2024); Current Understanding and Future Research Direction for Estimating the Postmortem Interval: A Systematic Review (Strete G et al.) (Diagnostics (MDPI), 2025).
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Representative model, for educational purposes only.