Some time ago, cybersecurity experts warned that smart phone pictures were now of a quality high enough for criminals to lift fingerprints of a peace sign and unlock a smart phone with them . Well, now the shoe is on the other foot (or more precisely: the glove is on the other side) as the police in south Wales have used a grainy one-hand WhatsApp photograph holding ecstasy tablets to successfully arrest a drug dealer.
With WhatsApp using end-to-end encryption, it was not about intercepting a message, but the South Wales Police found the photograph on the phone of someone arrested in Bridgend. "He had several texts like" What do you want to buy? "In him," Dave Thomas of the South Wales Police Science Support Unit told him to the BBC .
"There was then the photograph of the hand holding pills that looked like it was sent to potential customers saying 'these are my products, I'm selling them'. But I did not think they showed part of their hand and potentially there was a fingerprint. "
That does not tell the whole story – the image in question in The BBC website has a fairly low quality, and the top of the finger is covered, which is unfortunate, since that is the part that is stored in the national fingerprint databases. As such, there was no coincidence, but there was enough evidence to corroborate that the police had a suspect in mind, and by raiding the house and comparing again, they believe they have the right man: "While the scale and quality of the photography proved to be a challenge, the small pieces were enough to prove that he was the distributor. "
Beyond reasonable doubt?
If that makes you feel a little uncomfortable, it's for a very good reason. Although we were taught to believe that fingerprints are unique, we simply do not know for sure. And while in this case the corroborating evidence turned out to be decisive, that is not entirely reassuring as a precedent for less clear cases since it has been shown that contextual bias influences fingerprint examiners. In addition, as notes Gizmodo a 2011 study found that even in perfect laboratory conditions, mistakes can be made: of 169 fingerprint examiners, 3% made a false positive and 85% made a false negative.  And to be clear, this case was far from the perfect conditions of the laboratory: I have already linked to the photograph in question, but it is worth having another look with the previous paragraph in mind.
Still, the South Wales police are feeling within reach of this victory, and Thomas is anxious to see if other cases can be deciphered this way: "Now he has opened the floodgates and when there is a part of a hand in a photograph, the officers are sending them "
And that's just the beginning. "We want to be in a situation where there is a robbery at 20:30, we can scan the evidence and by 20:45 we can wait at the delinquent's door and arrest them by coming home with the loot," he added.
An important first step to that plan could include not encouraging criminals by telling the most-read news site in the UK that they are now looking at confiscated phones for fingerprint photographs, of course. Gloves are a cheap and low-tech form of security, but they certainly do the job, as thieves have discovered for decades.