Device reveals latent fingerprints on thermal paper

Engineers in Wiltshire have helped to develop and commercialise a device that reveals latent fingerprints from thermal paper in minutes.

Zeals-based Consolite Forensics worked with Dr John Bond, a senior lecturer in forensic sciences at Leicester University and former head of forensic sciences with Northamptonshire police, to develop the Hot Print System (HPS), a patent-pending device that that is quick and simple to use, requires no pre-processing or chemical treatment of samples, and is effective on latent fingerprints that are up to two years old.

Thermal paper is commonly used to print receipts, and these are often left in vehicles left at a crime scene.

Traditionally, chemicals would be used to reveal prints on the paper but lab tests are relatively costly and can lead to the paper becoming blackened, which entirely eliminates recovery of the fingerprint.

Operating at 96V – 264V AC and resembling a small desktop scanner, the 4kg HPS requires an operator to place the thermal paper with a suspected fingerprint into the device in order for a heat plate to gently warm the sample.

The sample is rapidly cooled once the system’s optical sensors detect a fingerprint, which is then preserved but can be redeveloped if required.

James Price, sales engineer at Consolite Forensic, explained the HPS only works on thermal paper because the inks embedded in it are activated by heat.

‘What we’ve found is that the sweat can react with the inks in the paper to make them unstable,’ he said. ‘As you gently heat up the paper you can develop the unstable areas…you can get a good contrast, you don’t blacken it.’

Price added that HPS – designed and built in-house and manufactured in the UK – has so far been sold to customers from America, the Middle East, China, and Australia.