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When a body is found, forensic scientists spring into action in an attempt to figure out the time and cause of death. At the moment, we often use simple temperature measurements to determine when someone died, but a new mathematical model could provide more accurate answers.
Maurice Aalders at the University of Amsterdam, the Netherlands, and his colleagues developed the new approach, which uses data collected from the scene where a body is found to create a 3D computer simulation. Skin and air temperatures, body size and position, and details of any clothing all feed into the model, which is then split into a matrix of cubes.
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The model calculates the rate at which heat would be transferred between neighbouring cubes, according to the thermodynamic properties of the materials they are made up of – for example, clothing or skin. This provides an estimate of how much the temperature of the body has changed since death, which can be used to calculate the elapsed time.
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Aalders and his team tested their method on four deceased subjects who had donated their bodies to research, with time since death ranging from 5 to 50 hours. The group compared its estimates with those produced using the standard and most widely used method to determine death at crime scenes, which relies on measurements of rectal body temperature.
The team found that the model was within 38 minutes of the true time elapsed since death, whereas the standard method gives estimates within 3 to 7 hours for the post-mortem interval (PMI).
“Their results suggest that they can predict PMI to within 1 hour of the actual PMI, which is considerably better than the best estimates produced by the most commonly used invasive temperature-based methods,” says Anna Williams at the University of Huddersfield, UK.
The new method is “ground breaking in the use of technology”, says Graham Williams at Staffordshire University, UK. “It is brilliant that the researchers were able to validate this model using real human corpses,” he says, rather than using animal corpses that would give less accurate readings.
“The next step now is to bring it to the crime scenes,” says Aalders. He says the method is going to be tested further at crime scenes in the Netherlands but won’t yet be used as evidence in court.
Journal reference: Science Advances, DOI: 10.1126/sciadv.aba4243
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