Single fingerprint at a crime scene detects class A drug usage

In a paper published in Royal Society of Chemistry's Analyst journal, a team of researchers at the University of Surrey, in collaboration with the National Centre of Excellence in Mass Spectrometry Imaging at the National Physical Laboratory (NPL) and Ionoptika Ltd reveal how they have been able to identify the differences between the fingerprints of people who touched cocaine compared with those who have ingested the drug -- even if the hands are not washed. The smart science behind the advance is the mass spectrometry imaging tools applied to the detection of cocaine and its metabolites in fingerprints.

This is a step up from research previously conducted by the University. In 2020 Surrey researchers were able to determine the difference between touch and ingestion if someone had washed their hands prior to giving a sample. Given that a suspect at a crime scene is unlikely to wash their hands before leaving fingerprints, these new findings are a significant advantage to crime forensics.

The Surrey team have continued to use their world-leading experimental fingerprint drug testing approach based on high resolution mass spectrometry. Cocaine and its primary metabolite -- benzoylecgonine*, can be imaged in fingerprints produced after either ingestion or contact with cocaine using these techniques. By analysing the images of cocaine and its metabolite in a fingerprint, and exploring the relationship between these molecules and the fingerprint ridges, it is possible to tell the difference between a person who has ingested a drug, and someone who has only touched it.

Dr Melanie Bailey, Reader in Forensic and Analytical Science and EPSRC Fellow at the University of Surrey, said: "Over the decades, fingerprinting technology has provided forensics with a great deal of information about gender and medication. Now, these new findings will inform forensics further when it comes to determining the use of class A drugs.

"In forensic science being able to understand more about the circumstances under which a fingerprint was deposited at a crime scene is important. This gives us the opportunity to reconstruct more detailed information from crime scenes in the future. The new research demonstrates that this is possible for the first time using high resolution mass spectrometry techniques."

Dr Allen Bellew, Applications & Marketing Manager at Ionoptika, commented: "To image these metabolites excreted through the skin requires very powerful analytical tools such as the unique Water Cluster Source that Ionoptika has been developing for over a decade. It's clear that this new technique will be important for forensic science in the future, and as a small business in the UK it's very exciting to see the role that our J105 SIMS instrument has played in its development."

Dr Chelsea Nikula, Higher Research Scientist, NPL said: "This novel application of three different techniques illustrates the capabilities of mass spectrometry imaging to enable next generation forensics analyses. It is great to see that the work we do here at NPL and the facilities we have available to us at the National Centre of Excellence in Mass Spectrometry Imaging helped support this research."

*Benzoylecgonine is a molecule produced in the body when cocaine is ingested, and it is essential in distinguishing those who have consumed the class A drug from those who have handled it.