Current time-of-death estimates are calculated by inserting a rectal thermometer into the corpse and comparing the result to a chart based on body weight and the area’s climate. The charts used do not even take into account different types of body structure. Not to mention insertion of the rectal thermometer could potentially destroy trace evidence.
New techniques use a non-invasive method by determining body temperature using thermal imaging or sensors attached directly to the body, then comparing them to a chart, taking into consideration such aspects as the amount of body fat, whether the victim was clothed, partially submerged in water, and several other factors.
“In our study, we achieve an accuracy of 45 minutes on average of people who are dead 5 to 50 hours,” said Aalders. “This is a major step forward in forensic investigations at the crime scene, where an inanimate body has been found. Our method can be used up to two days after the victim’s death.”
Computers are being used to re-create 3D images of the crime scene to help investigators.
Said Aalders: “Obviously we want to refine this further. We are convinced that it can be done even more accurately. But this improvement is already useful to the police. We are working on a method with which we capture a body at the crime scene 3D. That method, structure from motion photogrammetry, means that photography is taken from all directions, with which a program makes a 3D model. This is immediately read into our program to calculate the cooling. In this way, investigators can determine the time of death even more accurately for a variety of bodies, postures and situations.”
The database used in the new method has been tested against controlled conditions. Full results of the study can be found in the journal Science Advances.
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