Skin temperature and thermodynamic models allow to specify a time of death on the spot

Scientists from the Netherlands have proposed a method of determining time of death, which involves the measurement of the skin temperature and not of the rectum or of the brain, reported in Science Advances. The new method involves thermodynamic calculations that work if the death occurred in “non-standard” conditions, and predicts the time of death with precision up to 38 minutes instead of 3-7 hours, as earlier methods.

To restore the picture of crime, it is important to understand at what point in the death of the victim, if any. Time of death, if the death occurred a few days ago, determined by the degree of decomposition of a corpse with an eye on the conditions in which he was (patterns of decay under different circumstances studying at the “farms of corpses”). This may take samples of different tissues and to analyze what the decay products and how much they have accumulated, what insects have colonized the body, and so on. This involves working in a laboratory and allows to determine the time of death right at the scene.

As long as the body is still warm to ambient temperature, it is possible to use the nomogram Henssge. They are based on the thermometer, introduced rectally (in some other models it is proposed to use the testimony for the brain) and based on the fact that the body of a given mass at a constant ambient temperature cools with a certain constant speed. If the temperature is sharply changed and (or) the corpse was in something dressed, entered correction factors. The more time that has passed since death, the less accurate readings, calculated by nomograms: standard deviation ranging from 2.8 to 7 hours.

Alders Maurice (Maurice C. G. Aalders) and his colleagues from the University of Amsterdam and the Netherlands Institute of forensic medicine suggested that a more accurate way of establishing time of death based on body temperature. Contact thermometers, they determined the skin temperature of forehead, chest, belly and thighs of four bodies of men and women 60-94 years, who were in the morgue of the University of Amsterdam (and to death I agreed to donate bodies to science). The measurements were made from 5 to 50 hours after the death of the donor. Clothing on the bodies were made of cotton, their length ranged from 157 to 181 cm, weight — from 39 to 99 kilograms, percentage of body fat from 21 to 34 percent.

The researchers took the shape of the head for the ellipsoid, limb — over cones, torso and neck — for the cylinders. For each element modeled, the cooling time, knowing the thermal conductivity of fat, nairboi fabric and cotton. The ratio of their volumes calculated, knowing the standard proportions of the human body. The predicted temperature values are compared with observed in practice.

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