Scottish police have paired up with forensics experts from the University of Abertay Dundee to make lifting fingerprints from fabric possible for the first time. The technique, which has been around since the 1970’s, was only usable on smooth surfaces. But researchers have now figured out a way to use it on fabric.
Specifically, the process is called vacuum metal deposition (VMD) and works like this: Forensics scientists put fabrics into a vacuum chamber, where gold can be evaporated and spread evenly as a thin film onto the material. Then they do the same thing with zinc, which attaches to the gold only in areas that haven’t been touched by hands. The final picture looks like a film negative, revealing the miniscule skin ridges that form the characteristic whorls, loops and arches of a hand or fingerprint.
If you’re like me, you might think looking for fingerprints at a crime scene is a dated technique, more of a hassle than anything. Isn’t DNA fingerprinting far more accurate and sophisticated anyway? In reality though, fingerprints are still lifted at many crime scenes and offer clues beyond just identification of a perpetrator. The placement and orientation of prints on doors, windows or other surfaces can offer insights about what was going on and how and event unfolded — did the perpretrator climb out of the window? Why was he looking through the closet or the medicine cabinet?
So the more prints, the more clues. And lifting prints off fabric opens up a whole new set of information. Moreover, as Scottish fingerprint expert Paul Deacon put it in the university’s news release, “Fingerprints left on fabric and other surfaces can leave DNA traces, so it can also help forensic scientists to visualise the best area to target on an item of clothing to recover DNA evidence.”
Because the researchers only classify about 20 percent of people as “good donors” for fabric print-lifting, this attribute along with the potential to piece together a time line from the scene might prove to be the real strength of the technique. And if VMD is already an established method of getting prints, I can’t see a drawback to applying it to more materials from a crime scene — the more puzzle pieces, the better.