​Adding a third dimension to fingerprints

TU Delft and the Netherlands Forensic Institute (NFI) are developing a device that must help unravel the chemical signature of fingerprints.

When someone leaves a fingerprint at a crime scene, that person leaves more than just an impression of the friction ridges of the top of the finger. In the marking, a chemical signature is hidden which, if unraveled, could help solve the crime. It consists of a myriad of molecules that belong to the potential perpetrator, ranging from DNA, proteins, fats to amino acids and even metabolites of cocaine.

Unfortunately, this signature is hard to extract and analyze, especially at the crime scene itself. Sawing out pieces of a table or another type furniture with fingerprints on it for subsequent lab analysis is elaborate and may destroy other potentially interesting artifacts. Since the appropriate tools for chemical analysis are missing at present, fingerprints are usually only photographed.

Fingerprint expert Marcel de Puit of the Netherlands Forensic Institute believes he has the answer to the problem. He is working on a device that will enable forensic researchers to extract biochemicals from fingerprints right at the crime scene. He recently received two hundred thousand euros from the The Hague Security Delta (a consortium of businesses, governmental bodies, and knowledge institutions). He will further develop a prototype with a post doctoral researcher of the organic materials and interfaces section of the Faculty of Applied Sciences. The researcher, who will be hired soon, will be supervised by surface chemistry expert Prof. Ernst Sudholter and De Puit

The device looks somewhat like a pencil and is called the Mitra. It was developed by Phenomenex, a manufacturer of lab equipment, to improve the neonatal heel prick. Mitra allows medics to extract exactly 0.01 milliliter of blood. The fact that this little apparatus can suck up such a tiny and well-defined amount of liquid could also make it useful for forensics, the inventor of the Mitra thought. He sought contact with the Netherlands Forensics Institute.

“It is a brilliant invention that could become a game changer in forensics”, says De Puit. He wants to modify the tip of the Mitra in such a way that it acts as a sensor that reacts to the biochemicals on the fingerprint and determines what types of molecules are present. Another option is to collect tiny amounts of chemicals with the Mitra for analysis in the lab. “In both cases”, says De Puit, “we add a third dimension to fingerprints.”

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