Science & Technology

Engineering the CSI: Fingerprint Extraction using Amino Acids

Note: This article is hosted here for archival purposes only. It does not necessarily represent the values of the Iron Warrior or Waterloo Engineering Society in the present day.

Remember those old CSI re-runs where every piece of hair was a clue to the killer’s identity, and fingerprints were the ultimate weapon for condemning a murderer? Remember what came next? I.e., all the pissed off detectives and real crime scene investigators who started ranting about how no murder investigation could ever catch a criminal as well as the TV could, and how all these primetime dramas were convoluting the public’s knowledge of crime scene investigations to the point that criminal court cases were being affected? To an extent, this is still true—no crime scene is ever going to that exact piece of salivary evidence or DNA or footprint that you’re looking for. However, recently, scientists have found a way to enhance the collection of fingerprints (and it’s not by increasing image resolution).

The traditional methods of discovering fingerprints from old evidence are fuming and dusting. With fuming, fingerprints are recovered from old pieces of material, and they are placed in a jar of iodine crystals or cyanoacrylate. The fingerprint is then left to ‘develop’ over the course of a few hours. With dusting, fingerprints are lightly dusted with special powder, and then recovered with clear tape. Neither of these methods is effective at extracting dry and weak fingerprints.

A revolutionary method has been developed by Dr. Xanthe Splinter and her team at the University of Sydney in Australia. The team uses a combination of nanoparticle binding on the amino acids present in fingerprint traces to isolate the print.

Amino acids are the individual constituents of proteins. Since protein is produced by virtually every cell of the body, and fingerprints are left behind due to sweat, amino acids are always left behind on fingerprints. The concept of using amino acids had been developed since the 1950s, but limitations due to the sensitivity of amino acids on non-porous surfaces have restricted the large-scale implementation of this method.

Dr. Splinter has found a way to link amino acid-binding antibodies to gold nanoparticles, by working with a proof-of-concept immunologic reagent. These nanoparticles, which are now effectively ‘stuck’ onto the fingerprint, provide sharper detail when retrieving these prints.

“We’ve been able to successfully target amino acids on non-porous surfaces for the first time, with promising results in enhancing aged and degraded fingermarks that typically give poor results with traditional powdering,” said Splinter.

Splinter is now at work to complete the ultimate fingerprint-retrieval dream, which is to isolate prints from human skin. Due to the highly porous nature of the skin, isolating fingerprints has been extremely difficult to do. Completing this challenge would be the “holy grail” for fingerprint analysis.

It is always difficult to pinpoint every single piece of evidence needed to solve a case. Nevertheless, the new method brings potential to revisit unsolved evidence and old cases to see if any new evidence can be recovered. Spliner and her team hope to work with the Australian Federal Police to dramatically change the face of law enforcement. But Splinter’s work provides inspiration that you too, as an engineer, can live that long-buried dream of being a CSI—or helping them, anyway.

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