Bioanalysis Zone

Fingerprints: biological samples for identification of sex and, potentially, more

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The sweat of females is known to contain roughly double the levels of amino acids and a different distribution when compared with their male counterparts. Using this concept, a research group led by Assistant Chemistry Professor Jan Halámek at the University at Albany (NY, USA) has devised a technique through which fingerprint identify can distinguish sex.

Traditionally, fingerprinting has been used as a reliable identification method based on comparison of the physical image itself. But the dependence of the technique on pre-recorded matching fingerprints has proven to be a limitation. By focusing on the biochemical content in fingerprints using a biocatalytic assay coupled to a specially designed extraction protocol, the research group has shown that fingerprints can effectively act as biological samples and identify the sex of the individual.

The group developed a method to extract the amino acids from fingerprints by transferring them onto polythene films, followed by placing a drop of diluted hydrochloric acid solution on the prints and applying heat. This induced the water-soluble amino acids to migrate into the solution. The extracted amino acids were then measured using a colorimetric test.

The procedure was first tested on mimicked fingerprint samples, 50 amino acid mixtures randomly generated to represent male and female fingerprint composition characteristics, which was found to have 99% accuracy in the correct classification of sex. The group then successfully tested the procedure on real fingerprints of both sexes, and on fingerprints taken from five different surfaces.

“One of the main goals for this project was to move toward looking at the chemical content within the fingerprint, as opposed to relying on simply the fingerprint image,” commented Halámek. “We do not intend to compete with DNA analysis or the databases used for identification. Instead we are aiming at differentiating between demographic groups, and more importantly, we are aiming at making use of fingerprints that are smudged/distorted or that don’t have an existing match.”

Halámek hopes to extend his research and is in the process of developing identification techniques to improve the scope of fingerprints in forensic analysis.

Sources: Chemist’s technique can identify a fingerprint as male or female. Huynh C, Brunelle E, Halámková L, Agudelo J, Halámek J. Forensic Identification of gender from fingerprints. Anal. Chem. 87(22), 11531–11536 (2015).

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