The chance that the police can nab a murderer increases significantly if the time of death of the victim is known. Researchers at the Amsterdam UMC, Netherlands Forensic Institute (NFI), the police and TU Delft have designed a new calculation model and associated equipment which allows forensic experts at the crime scene to determine the time of a crime to within 45 minutes.
This is a significant improvement as detectives now often have to work with windows of three to six hours. The model is expected to be in use as early as this summer.
The time of death is determined by the body temperature of the remains and depends on the cooling rate. The cooling rate in turn depends on the physical build of the victim, his/her position and a lot of surrounding environmental conditions. These can range tremendously. The model that the police now use – the Henssge model to determine the postmortem interval – takes little account of all the variables. “It assumes a standard body of a standard weight under standard circumstances,” says Martin Roos of the NFI. He is the project leader of the research project called ‘Therminus’.
First you map the entire body in 3D
The input for the models thus needs to be much more accurate. With the new system, researchers will first map the entire body in 3D at the crime scene. “We will photograph the entire body,” explains Maurice Aalders of Amsterdam UMC. “This can be done with a regular camera or even with a phone. The photos of the body can then be uploaded in a software programme that uses the photos to generate a 3D model of the body. You then know the exact dimensions of the body.”
But you are not quite there yet. “You also need to weigh the victim,” says Arjo Loeve of the Medical Instruments & Bio-inspired Technology (3mE) research group that is also involved in the project. “This can be done fairly easily in a mortuary, but you really want to know the weight as quickly as possible so you can input the details in the model immediately. Every minute counts. The faster the police know the time of death, the more targetted they can close the escape routes.”
The remains are transported in a body bag or on a simple trolley or – if the body is in a bad state – a sort of sarcophagus, a two-part plastic container. Loeve and his colleagues have made a measuring instrument that works with all these types of carriers.
Registering the slant angles
Bodies are usually kept in a horizontal position when being weighed. But in practice this can be challenging. People who carry the coffin are not always the same height and the ground is not always even. “Our weighing scales accounts for this,” says Loeve. “It consists of two modules that communicate with each other. Each weighs a part of the body and registers the slant angle.”
Another factor that determines the speed at which a body cools down is the amount and type of clothing. The insulating values of clothing can also be estimated and processed in models. This is a rudimentary technique. Loeve continues. “Now people for instance check if the person’s sweater is cotton or wool. They then estimate the value. But this technique does not deliver reliable estimates. You also need to look at whether the textile is damp and how compressed it is. A comfortable spacious woollen sweater insulates better than one that is completely compressed. We have made a useful device that can determine the heat conduction coefficients of pieces of clothing. It does this in the police bus within 15 minutes.”