The UK's finger and palm-print database, Ident1, has more than seven million sets in its archive. Each time someone comes into contact with the police, their prints are collected and uploaded, to be cross-referenced with those found at crime scenes.
"Fingerprints are one of the few types of evidence that can tie the trace to an individual," says Stephen Bleay, a government scientist at the Home Office's Centre for Applied Science and Technology (Cast). “Within the UK we still have more fingerprint identifications than we do DNA”.
Read more: The new pound coin is here – and it's so high-tech, it's 'impossible' to fake
Paper holds fingerprints well, so banknotes have long been one of the best places for police to find them. But the Bank of England is moving away from paper – it's already introduced a polymer fiver, and a similar £10 note, featuring Jane Austen, is due in September.
The introduction of the new £10 note poses a real problem for fingerprinting. “If you're doing a drugs deal it’s not two or three fivers you are handing over, it is a £10 or £20,” says Bleay, 51. So the team at CAST is testing a new method of pulling identifying information from the new polymer notes using a combination of magnetic powder, infrared imaging, and a gel.
The technique was originally developed for the plastic £5 note – and at first it proved hard to apply. "The new notes have lots of different materials and surface treatments within a small space," says Bleay. "A fingerprint on that doesn't interact the same on each of those regions." That's why the team at Cast has spent three years working with the Bank of England to perfect a new method that will work across different materials.
First, metallic fingerprinting powder – known simply as black powder – is applied to an iron bar with a magnet at the end and sticks like bristles, which creates a kind of "brush" (above). Then metallic particles are painted onto the note, so it can be viewed with an infrared imager. "The fingerprint's adhesive nature makes the particles stick," Bleay explains.
Not all fingerprints leave the same level of traces. If the prints cannot be seen, a tacky gelatine material can be used to lift the powder from the note's surface. Infrared is then used to view fingerprints on the gel. The entire process can be completed in less than an hour, Bleay says: "You could do it at a crime scene."
The new technique will be included in the Home Office’s almost 900-page Manual of Fingerprint Development Techniques – first published in 1986. But although 200-person CAST is prepared for widespread use of plastic, until all the paper notes are replaced, Bleay and his team have to keep ahead of the law. “If the solvents we use for the paper processing come under the legislation of ozone depleting solvents,” he says, “we will have to do a major reformulation.” Paper isn’t dead just yet.
This article is due to be published in the September 2017 issue of WIRED
This article was originally published by WIRED UK
