No trace to lose: improving crime detection with more effective trace analyses ​​​​​

Sometimes, fingerprints or DNA are left behind at a crime scene. Sometimes, these are the result of innocent activities or left by chance. Can you distinguish traces of a crime from traces of everyday activities? In addition to tackling this big question, researchers from the Netherlands Police Academy and Amsterdam University of Applied Sciences are looking into how best to secure traces to preserve all information. In collaboration with the criminal justice chain, including the police, the Public Prosecution Service, and the Netherlands Forensic Institute (NFI), this international study is being launched to improve the search, packaging, transport, and interpretation of traces. 

In the new four-year 'No Trace to Lose' project of the Netherlands Police Academy and Amsterdam University of Applied Sciences, researchers are tackling some major issues in forensic investigations. 

Was a trace left after a crime, or is there another explanation? 

There are often numerous traces found at a crime scene, such as DNA and fingerprints. But how did they get there? Are they the result of a crime committed there (crime-related) or could they have been left there in another way and at another time? New technologies have made forensic investigators increasingly better at analysing and interpreting small traces. That offers advantages in tracking down possible perpetrators, but it also results in many traces being found of people and activities unrelated to the crime. 

The researchers want to better understand this vast array of traces. That is why they are examining which tracks end up where after different types of activities. "By re-enacting crime scenarios and everyday actions in Netherlands Police Academy practice houses, we are looking at which DNA traces or fingerprints are left in which places during which activities. We also look at this in real homes. Which are the crime-related traces and the background traces of residents and visitors? And how many traces do you find of people who have not been there but were transferred by a chance touch on the train? We want to know how likely it is that a trace is 'interference’ or a crime-related trace," says Christianne de Poot, lecturer in Forensic Research at theNetherlands Police Academy and Amsterdam University of Applied Sciences. 

There are often several explanations for traces at a crime scene. Suspects often provide alternative explanations for the presence of their traces at a crime scene. Can that statement be true? And how likely is that statement to be true? De Poot: "To test it, you need to know whether you can distinguish between crime-related and other traces. Knowledge of this not only helps in testing scenarios during evidence but also helps search for relevant traces at the crime scene." 

Packing and transporting objects with traces 

The other big question in crime detection is about securing traces. In an international comparative study, researchers are considering the best procedure for packing and transporting objects containing traces, known as trace carriers. De Poot explains: "If a trace carrier is found at a crime scene, you must treat it with integrity. Especially if information about activities is derived from it. The next piece of important information is exactly where the trace was left, and that information should be preserved. Could trace evidence be disturbed by the current method of packaging and transport? And do we perhaps lose important trace information as a result? With practical observations, comparisons between units, and procedures used abroad, we are looking at how best to pack and transport trace carriers to preserve all trace information."

"We also want to find out whether it is better to do the sampling at the crime scene instead of packaging and transporting items before sampling and analysing them later, in the lab. The latter procedure now seems to be dictated by time constraints. Non-moveable items, such as a sofa, are sampled at the crime scene, but smaller items are generally taken and sampled in the lab," de Poot explains. There is a chance that direct sampling could lead to better results for certain objects, as less material and less information would be lost during packaging and transportation.   

Cooperation 

This research involves the entire criminal justice chain: the Netherlands Police, the Public Prosecution Service, the judiciary, and there is intensive cooperation with the NFI, which does much of the DNA testing for the experiments. De Poot: "As early as during the research, we will share conclusions directly with practitioners and educators. We also collaborate internationally with the University of Lausanne and the Victoria Police Department, among others, as they have plenty of expertise in this field." The legal profession is also involved in the study. "We think lawyers can ask relevant questions. In their defence, they often offer alternative explanations for the presence of a suspect’s traces on a trace carrier or at a crime scene. It is important to be able to test those statements," De Poot concludes. 

More information

• More on the 'No trace to lose' study
• Personal page of Christianne de Poot