Sunday, November 29, 2020

RCMP shine light on latest fingerprint-detection methods for new polymer banknotes

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Michael Whyte
Crime Scene Officer and Fingerprint Expert with over 7 years experience in Crime Scene Investigation and Latent Print Analysis. The opinions or assertions contained on this site are the private views of the author and are not to be construed as those of any professional organisation or policing body.
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When the Bank of Canada started making the switch a few years ago from paper currency to the smoother polymer bills, it touted the upgrade as a way to stay ahead of counterfeiters.

But the change also meant that Canada’s crime fighters had to come up with a new method for lifting fingerprints off of them since the traditional “wet chemistry” method used on the old paper bills no longer worked on the new ones.

A team of RCMP forensic scientists has now developed a protocol using some nifty gadgets that have shown promise for detecting fingerprints off cold-case exhibits that may have been in storage for years.

“We have full confidence that when high-profile cases are coming to our forensic identification sections, we know what the best approach will be,” said Della Wilkinson, a research scientist with the RCMP’s Integrated Forensic Identification Services in Ottawa.

The need to lift fingerprints off of money happens in all sorts of investigations, from residential break-ins to drug investigations to kidnappings involving ransoms, Wilkinson said. “Who’s handled that (money) becomes very key in tying people to the event,” she said.

In the old days of paper money, investigators would dip the bill in a chemical solution. That would cause a reaction with sweat and oil residue from the finger, allowing investigators to visualize the print wearing special goggles and using blue-green lights in a dark room.

When RCMP forensic scientists heard that the Bank of Canada was going to begin rolling out new polymer bills, they knew that this method wouldn’t work on the new bills.

They started consulting with their counterparts in Australia, which had introduced polymer bills years earlier, and also worked out a deal with the Bank of Canada to start doing tests on the new polymer bills before they went into circulation.

“We were very lucky to be loaned banknotes from the Bank of Canada for this research,” Wilkinson said. “It allowed us to be ready by the time the notes were turning up at crime scenes.”

The recommended RCMP protocol for detecting fingerprints on polymer banknotes was adopted this year and published in the Journal of Forensic Identification by Wilkinson and colleague Rolanda Lam.

The protocol recommends that investigators start with the most accessible method — the cyanoacrylate fuming method, also known as the superglue method.

The polymer bill is placed inside an airtight chamber. The humidity level is raised to about 80 per cent.

Superglue is heated, transforming it from a liquid to a vapour. A fan distributes the vapour throughout the chamber and when it comes into contact with fingerprint residue, it causes a chemical reaction, making the print more visible.

But there is a limitation with this method. Fingerprints can be detected easily only on the transparent parts of the banknotes. It is harder to visualize them on the opaque, or ink-covered, parts of the bill.

In this instance, investigators are told to then try another method: vacuum metal deposition, or VMD.

The RCMP has identified vacuum metal deposition as a reliable way of detecting fingerprints from polymer bills. In this photo, polymer banknotes are shown loaded into a vacuum metal deposition chamber. (Image RCMP)

Again, the bill is placed inside a special chamber. Minute gold filings are vaporized, coating everything inside the chamber. The gold is absorbed into the fats and oils of the fingerprint.

Then vaporized zinc, which features a reflective surface, is introduced. It sticks to the gold and nothing else, thus helping to visualize the fingerprint.

Currently, the RCMP only has one older-generation VMD chamber located in Ottawa, but the introduction of polymer banknotes has prompted the agency to look into acquiring three new machines from a U.K. company for its detachments in Surrey, B.C., Newmarket, Ont., and Montreal, Wilkinson said.

They aren’t cheap — costing about $350,000 each. But in a report this past June to Surrey City Council touting the benefits of VMD technology, Chief Supt. Bill Fordy said it was the “most sensitive technology for obtaining fingerprints on solid (non-porous) objects presently available in forensic science.”

It can be used to find prints on plastic packaging, plastic bottles, glass, tight-weave fabrics, firearms, glossy paper or magazines, Fordy said. The technology was even able to turn up a fingerprint from an exhibit in a 17-year-old homicide in Alberta.

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