The burden of proof of a fingerprint or bloodstain found at a crime scene is significantly increased if the police know when the traces were deposited. For this reason, a team of researchers from the Department of Forensic Medicine at Aarhus University will now lead the way in the development of a method to date biological traces. The project has received almost DKK 9 million in support from the Innovation Fund Denmark.

2019.12.16 | Henriette Stevnhøj

A fingerprint, a bloodstain or other biological material are some of the traces the police search for at a crime scene. With the help of the biological traces, a person or perpetrator can be tied to a crime scene. However, until now it has not been technically possible to determine when a fingerprint or other trace was made and thus determine whether it is relevant to the investigation.

Researchers from the Section of Forensic Chemistry and from the Bioinformatics Research Centre at Aarhus University are collaborating with researchers from the Department of Food Science at the University of Copenhagen, as well as the National Forensic Services at the Danish National Police, on the development of an analytical method that clarifies the age of biological traces. The method will potentially determines whether a person or perpetrator was at the scene at the time a crime was committed.

Determining the age of biological traces is not a new idea and it is probably one of the largest as yet unsatisfied needs in the field of modern forensic science.

“There have been many previous attempts to solve the problem, but in our assessment, advanced techniques and data processing methods have first now reached a level where we believe that this challenge can be resolved,” says Mogens Johannsen from the Section of Forensic Chemistry. Together with Kirstine Lykke, who is an engineer and PhD at the Section of Forensic Chemistry, he is behind the project which has been named TraceAge.

Categorising lawful and criminal traces

“In many criminal cases there are often imprints and traces from persons with a legitimate reason for being present at the crime scene at certain times. The new method will also help the police to determine whether an imprint left at a crime scene has anything specific to do with the actual investigation or not, thus enabling us to focus our work on the relevant traces,” says Stine Rasmussen, project manager at the National Forensic Services in the Danish National Police.

Another example could be bloodstains following acts of violence or murders. Here, it will be possible to get an indication of the timeline of the course of events for the crime. Currently, it is not always possible to determine this.

Knowledge of metabolites contributes

In the project, the researchers from the Department of Forensic Chemistry and the Department of Food Science use advanced measurement methods and data analysis techniques to obtain knowledge about the degradation time of substances and thus trace age.

A biological trace from a fingerprint or a bloodstain consists of a complex combination of substances, each of which degrades at differing rates over time. The researchers’ goal is to identify the substances and their degradation products and to develop an analytic method that can measure the amounts and determine the age of the trace.

"With our analytical equipment, we can measure many substances at once, and by conducting tests on fingerprints and bloodstains we can follow their degradation over time. Temperature, humidity, light, surfaces and similar have an influence on the rate of degradation, and we test different conditions to examine which substances are the most robust for age determination,” says Kirstine Lykke Nielsen.

In some ways, the biological degradation of fingerprints and blood is the same as when foods are being stored, and this is why Professor Søren Balling Engelsen the Department of Food Science is also involved in the project.

Large amounts of data analysed

Based on the extensive amounts of data collected about rates of degradation and the formation of degradation products, the researchers will develop a model that can determine the age of a trace.

Both the Department of Food Science at the University of Copenhagen and the Bioinformatics Research Centre at Aarhus University have experts who can extract useable information out of large amounts of data.

“The measurements generate a great deal of data and this requires advanced data processing method utilising “machine learning” to analyse this data and develop models that can determine the age of unknown traces,” says Palle Villesen from the Bioinformatics Research Centre.

The primary user of the new method will be the National Forensic Services, which provides forensic support services to the police districts in Denmark. The National Forensic Services examines almost 9,500 fingerprints and nearly 2,000 bloodstains every year. It would be particularly relevant to use the method in cases with bloodstains as they are often characterised by being serious and indicating bodily harm.

The Innovation Fund Denmark has invested DKK 8.6 million. The total budget for the project is DKK 13 million and t he method is expected to be ready for use in 2022.

Contact

Engineer, PhD, Kirstine Lykke Nielsen
Section of Forensic Chemistry, Department of Forensic Medicine, Aarhus University
Mobile: (+45) 2275 1684
klyn@forens.au.dk

Professor Mogens Johannsen
Section of Forensic Chemistry, Department of Forensic Medicine, Aarhus University
Tel.: (+45) 8716 8332
mj@forens.au.dk