FORENSICSNew Method for Fingerprint Analysis Holds Great Promise
Overlapping and weak fingerprints pose challenges in criminal cases. A new study offers a solution and brings hope for using chemical residues in fingerprints for personal profiling.
A groundbreaking study has made it possible to extract much more information from fingerprints as evidence than what is currently achievable.
A new study from the Department of Forensic Medicine at Aarhus University is the first in the world to analyze fingerprints on gelatin lifters using chemical imaging. This could be crucial in criminal cases where current methods fall short.
Danish police frequently collect fingerprints at crime scenes using so-called gelatin lifters. Unlike tape, these lifters are easy to use and are suitable for lifting fingerprints from delicate surfaces, such as peeling wall paint, and irregular objects like door handles.
Once collected, the fingerprints are photographed digitally so they can be processed through fingerprint databases. However, traditional photography cannot separate overlapping fingerprints, which are often found at crime scenes. Very faint prints are also problematic. As a result, many fingerprints that could otherwise contribute to investigations unfortunately have to be discarded.
A Fine Spray of Solvent
A solution is presented in the new study from the Department of Forensic Medicine at Aarhus University, recently published in the scientific journal Analytical Chemistry.
“We are presenting a method that has the potential to be integrated into the police’s traditional workflow. If this happens, more fingerprints from crime scenes could be used and evaluated both visually and chemically,” says postdoc Kim Frisch, who is behind the study.
The method is based on a technique called Desorption Electrospray Ionization Mass Spectrometry (DESI-MS), which works by measuring the chemical compounds in fingerprints based on their mass.
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Collecting fingerprints
· For over 100 years, fingerprints have been used in criminal investigations and remain the most widely used physical evidence.
· Most fingerprints found at crime scenes are not immediately visible to the naked eye. Investigators must therefore develop the prints, for example, by dusting surfaces at the crime scene with colored powder that adheres to the fingerprints and makes them visible.
· Fingerprints are then lifted from the surface—often using gelatin lifters, which are flexible rubber sheets coated with a layer of gelatin that absorbs the fingerprint.
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“We send a very fine spray of solvent, consisting of electrically charged droplets of methanol. This releases and ionizes substances on the surface of the fingerprint on the gelatin lifter. The substances are then drawn into the instrument, where their masses are measured individually,” explains Kim Frisch.
