Our clothes could become witnesses in criminal investigations.
Researchers from the University of Abertay, Scotland, and the Scottish Police Services Authority (SPSA) are seeking to recover fingerprint details and ridge impressions using a technique known as vacuum metal deposition (VMD. The technique uses gold and zinc to recover the fingerprint mark and is already used to detect fingerprints on plastics, glass and other smooth surfaces.
Joanna Fraser, a forensic sciences researcher at the University of Abertay, said in the press release “The research uses fine layers of metals to display fingerprints people may have left on fabrics, something which is far harder to do with soft surfaces. The technique has been around since the 1970s and is used on many surfaces but was never widely used on fabrics.”
The process is similar to that of photographic negatives, where a colour will show up as it’s opposite. “We take these fabrics, place them in a vacuum chamber, then heat up gold to evaporate it and spread a fine film over the fabric.
“We then heat up zinc, which attaches to the gold where there are no fingerprint residues. This helps reveal the fingerprint – where contact has been made we see the original fabric, where there was no contact we’re left with the grey colour of the metal film.”
Until now it’s been difficult to reveal fingerprints on fabric. Paul Deacon, fingerprint unit manager at the Scottish Police Services Authority (SPSA) and one of the experts on the project said in the press release “Fingerprints have been used as a means of identification for over 100 years but recovering fingerprints from fabrics has always proven to be fairly difficult.
“The research is still in its early stages but we are starting to see results. We have shown that fabrics with a high thread count are best for revealing a print and have recovered identifiable fingerprints on a number of fabrics including silk, nylon and polyester.”
So far only 20 percent of the public have been classed as good fingerprint donors, but the researchers have had success with revealing the shape of handprints on fabric. Paul Deacon said “Such an impression could help the police piece together a timeline of events and could be used to provide evidence in cases where someone was pushed, or grabbed, in a particular area of their clothing.
“For example, an impression of a palm print on the back of someone’s shirt might indicate they were pushed off a balcony, rather than jumping. 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.”