Investigators at Amsterdam UMC have developed a new method to determine the time of death at a crime scene much more precisely. With the technique used currently, the uncertainty is several hours; this new research reduces it to less than an hour. The results of the study appear in Science Advances.
"In our study, we achieve an accuracy of 45 minutes on average for people who are dead for 5 to 50hours," says research leader Maurice Aalders, professor of Forensic Biophysics at Amsterdam UMC. “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. ”
Currently, the technical investigation department uses a simple model based on the temperature of a body after death.
“The temperature is determined rectally. Together with the body weight and the temperature in the environment, a table shows how many hours ago that person died. The temperature measurement method is not ideal, because the detective has to make an invasive measurement and thus destroy traces," said Aalders.
The table used by the police is also not ideal. This is based on the cooling of a body under standard conditions, conditions that can sometimes deviate. When cooling down, it makes a huge difference whether a person is heavily built or very thin.
“The results are not so reliable. In people of equal weight, but with different body structures, the model gives the same result," said Aalders.
Aalders and his researchers from Amsterdam UMC, in collaboration with the Co van Ledden Hulsebosch Center and the Netherlands Forensic Institute (NFI), have developed a more precise method to determine time of death.
In the new method, a crime scene detective non-invasively measures the temperature in one to four places with a thermal camera or a sensor that is attached to the body. The measurement data go into a model that is more precisely tailored to the situation with additional information: has the body been left clothed, is it (partly) in the water, on which surface has it been found, and so on.
This approach has been tested with bodies whose exact time of death is known. The researchers took into account the amount of body fat and the clothes the victim was wearing. On average, the deviations were 45 minutes, sometimes with a deviation of just over an hour. The results are much better than the old method.
“Obviously we want to refine this further,” says Aalders. “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."
Republished courtesy of Amsterdam UMC.