Germany’s largest national newpaper, Suddeutsche Zeitung, reports on Intelligent Fingerprinting’s innovative, fingerprint-based drug screening technique.
Fingerprints are more than just grooves
analysing fingerprints is one of the oldest forensic methods. Now, science is giving it a significant boost: With the help of nanoparticles, mass spectrographs, infrared rays, and color profiles, it is expected to reveal much more about a person than just their identity.
In many TV crime dramas, forensic investigators are now just as big stars as the detectives. This is mainly due to the fact that the “spy” investigators, in their white overalls and lab coats, use mysterious devices and high-tech methods to distill evidence from the most inconspicuous traces.
One of the oldest of these forensic methods, fingerprint analysis , is currently being significantly enhanced by science: With the help of nanoparticles, mass spectrographs , infrared rays , and color profiles, researchers are extracting far more from the seemingly simple fingerprint than the distinctive pattern of skin lines. They can determine, among other things, whether the print is even genuine and whether the suspect has handled explosives or taken drugs.
Intelligent Fingerprinting, a company based in Norwich, England, specialises in this area . It offers test kits that allow police not only to secure fingerprints but also to determine whether the person who took them has consumed cocaine, heroin, methadone, or cannabis. The company is currently working on a mobile device that enables drug testing by applying a finger to a person’s body. The fingerprint lines analysed in this process consist of a mixture of sebum, old skin cells, salts, and sweat.
All of this can reveal a lot about the physiology of the person who left the trace. “We believe this will allow for significant advances in crime prevention,” says David Russell , company founder and chemist at the University of East Anglia.
In the laboratory, Russell and his team coated gold nanoparticles with antibodies that specifically bind to drug metabolites. In a second step, they attached a fluorescent dye to the particles, causing the print they examined to shimmer in color. “This is proof that this person took and metabolised the drug,” the company website states. The resulting image was so clear that the researchers were even able to enlarge the skin pores, Russell writes in a recent review article on his and related methods in the journal Angewandte Chemie .
Substances that a suspect has only handled can be detected using other methods. Graham Cooks of Purdue University has developed the so-called DESI method for this purpose. In this method, the fingerprint is sprayed with electrically charged water droplets, which dissolve chemicals such as the explosive RDX from the grooved pattern. The droplets are then sucked into a mass spectrograph, which sorts molecules and detects the substances of interest.
In principle, a similar analysis is also possible under infrared illumination. This can trigger characteristic vibrations in the sebum molecules in the fingerprint, which are then altered by RDX residues. Images then show, for example, the grooves of the fingerprint in blue and grains of the explosive in red.
However, many of these and similar techniques are not yet fully developed for everyday police use. Either the devices are large and bulky, the analysis destroys the fingerprints, or they must be transferred to special materials before analysis is successful. However, researchers have already been able to isolate coffee, nicotine, painkillers, and narcotics from the traces, in addition to drugs and explosives.
Another scientific goal is to capture conventional fingerprints precisely and quickly. To this end, the German government is funding the ” Digi-Dak ” project, coordinated by Jana Dittmann at the University of Magdeburg. Researchers shine a special lamp with a precisely defined white light spectrum onto the fingerprints. Although these appear flat to the naked eye, microscopically they are a sequence of peaks and valleys. The measuring equipment can reconstruct this spatial structure from the different light colors produced by an irradiated fingerprint.
The resulting image is so precise that even individual sweat glands become visible. This allows fingerprint experts to solve a problem they created themselves. They had learned to print standardised artificial fingerprints for testing purposes. Now they wanted to prevent them from being mistaken for real fingerprints. The Digi-Dak project revealed that the grooves and valleys of the printed fingerprints were too uniform to be human.
