Researchers in Scotland may have just opened up a new avenue of forensic evidence for authorities to use: getting fingerprints off of clothing. Beyond just ID'ing someone, being able to see where hands were laid on a victim could reveal new information about a case.
To recover the fingerprints, researchers are experimenting with vacuum metal deposition, a technique that's already used to find prints on smooth surfaces such as plastic and glass:
The fabric is placed in a vacuum chamber. Gold is heated and evaporated and spread in a fine layer over the fabric. Heated zinc is then applied, which attaches to the gold layer where the fabric has no fingerprints, leaving the original fabric to show through where contact has been made.
It's a bit like a photographic negative, according to Joanna Fraser, a professor at Scotland's University of Abertay Dundee, which is working with the police there. "Here the fingerprint ridges show through as clear fabric, but where there are no ridges we see the distinctive gray color of the metal. Previously it had proved difficult to reveal a clear fingerprint on fabric, but we've shown that this is now possible." The challenge ahead, as identified by Fraser, is refining the process enough that a fingerprint is clearly visible. Right now, the team is seeing success one out of every five tries, and have found that fabrics with high thread counts, such as silk and polyester, work best.
Even without a clear print, the results are still useful to investigators. A suicide by jumping off of tall building, for instance, could be ruled a murder if, say, a hand print was found on the jumper's back, which could indicate the person was pushed off instead.