Analytical scientists from Loughborough University have made a groundbreaking discovery: drug residue, specifically the fast-acting sleeping pill Zolpidem—often linked to drug-facilitated sexual assault and drink spiking—can be detected on gel-lifted fingerprints.

Jim Reynolds and Ayoung Kim believe this advancement could provide new insights into cold cases and unsolved crimes. Forensic gel lifters, which transfer prints onto a gelatine surface, are widely used by crime scene officers to preserve and visualize fingerprints.

“This is the first time that analysis of gel-lifted prints for a drug substance has been accomplished. It shows that lifted prints and other forensic marks can yield valuable information,” said lead researcher Reynolds. “Since gel-lifted prints and marks can be stored for many years, this technique could be especially useful in cold cases, potentially linking or exonerating suspects. Collaborating with police forces to apply this method to cold case samples could help bring justice to criminals who thought they had escaped detection.”

Existing tests can detect drugs directly from fingerprints but have limitations—they can be destructive to the fingerprint, degrade drug residues, and be negatively affected by environmental interferences.

It has long been speculated that gel-lifted prints contain valuable chemical information and could offer more accurate drug detection. However, traditional techniques used to analyse the chemicals present in a sample have not been suitable for gel lifters because they detect all chemicals present, including those making up the gel, making it difficult to identify specific substances.

Reynolds and Kim overcame this issue with a method called sfPESI-MS, which uses a rapid separation mechanism to distinguish the drug substance from the background of the gel.

The process involves sampling the chemicals from the gel lifters into tiny liquid droplets, which are then ionized. The drug substance chemicals are more surface-active than the chemicals from the gel, enabling their separation from the mixture. This method allows for the direct detection of a drug substance using mass spectrometry.

“By linking chemical information to the fingerprint, we can identify the individual and link them to the handling of an illicit substance, which may prove useful in prosecution,” said Reynolds. “This could also help detect individuals who have been spiking drinks. If the drug they are using gets onto their fingertips, they will leave evidence at the scene.”

According to the published study in Drug Testing and Analysis, the researchers successfully tested the technique using Zolpidem-laced fingerprints lifted from glass, metal, and paper surfaces in a laboratory setting.

They now hope to work with police forces to analyse stored gel-lifted prints and use the method to identify other substances.

“Zolpidem was the focus of our research, but the method could just as easily be applied to other drug substances a person may have been handling and could be applied to other chemicals such as explosives, gunshot residues, paints, and dyes,” said Reynolds.

Original article

https://analyticalsciencejournals.onlinelibrary.wiley.com/doi/10.1002/dta.3688

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