Male or female: Gender fingerprinting
- Published: Dec 1, 2015
- Author: David Bradley
- Channels: UV/Vis Spectroscopy
US researchers have taken another step forward to make it easier for law enforcement to catch criminals from fingerprints. Building on an earlier tests that distinguish between blood samples from people of Caucasian and African-American ethnicity and males and females, the team has now demonstrated that they can tell whether a fingerprint belonged to a man or a woman using an optical technique.
Jan Halámek and his team (Crystal Huynh, Erica Brunelle, Lenka Halámková, Juliana Agudelo) at the University at Albany, State University of New York, have discovered a straightforward concept for identifying whether a suspect is male or female in order to eliminate people from a crime scene investigation. The optical technique used bases the determination on the content of the fingerprint rather than size, shape, or pattern – more specifically the levels of amino acids in the residue left behind with the print. It was already known that amino acid levels in the sweat of females are about twice as high as in males. There is also a slight difference in the distribution of particular amino acids, which is due in large part to hormonal differences between men and women. As such, the amino acids left behind in a fingerprint, could offer forensic evidence that was previously overlooked. "The contents of fingerprints can provide information in a way that is analogous to the contents of other body fluids such as blood," the team says.
Halámek's team was able to quickly and easily extract the amino acid content from a fingerprint that was transferred onto plastic film. Treatment with a hydrochloric acid solution followed by heating releases the amino acids into the acidic solution for testing. The test is based on a bioaffinity interaction between an enzyme and its ligand in order to generate a colour change that can be seen by the naked eye or spectroscopically quantified, the team says. They did a proof of principle experiment with "mimicked fingerprint samples" which demonstrated a 99 percent chance of accuracy in the determination of sex of the person who left the fingerprint. The next step was to simulate an actual crime scene scenario wherein a female volunteer placed three fingerprints on five different surfaces, including a doorknob and a computer screen. This proved that the extraction and the test itself were capable of extracting the amino acids from all surfaces tested and demonstrating that the fingerprints belonged to a woman.
Faster than DNA
"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," Halámek explains. "We do not intend to compete with DNA analysis or the databases used for identification. Instead we are aiming at differentiating between demographic groups directly on crime scene, where such simple test kits can be used by person without scientific background, and more importantly, we are aiming at making use of fingerprints that are smudged or otherwise distorted or that don’t have an existing match." This is a problem for crime scene investigators who often find partial fingerprints and smears that cannot be used to match to a recorded fingerprint pattern but will still contain identifiable information such as DNA and now, amino acids.
There has been much research using spectrometric and spectroscopic methods such as matrix-assisted laser desorption ionization (MALDI) and liquid chromatography-mass spectrometry (LC-MS) and infrared and Raman spectroscopy in investigations, but these complex and powerful techniques require complex and powerful instrumentation that is usually not portable. Halámek adds that this is just one more step towards the development of an arsenal of identification methods for use in investigations, but it is an important one with the potential to more quickly home in on a suspect or exclude the innocent without having to wait for DNA analysis before moving forward.
Anal Chem 2015, 87, 11531–11536: "Forensic Identification of Gender from Fingerprints"
Article by David Bradley
The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.
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