Fast-track DNA technology links rape suspects to a crime within two hours

It can also quickly match criminals to previous offences before they have to be released into the community where they could reoffend

Rapists are being caught by fast track DNA technology that can provide forensic matches within two hours before suspects have to be released from police custody.

The Met is among police forces trialling the technology, which is so fast that it links suspects to a crime or even previous offences before they have to be released after 24 hours into the community, where they could reoffend.

It has already been used to match suspects with unsolved “historic” sex assaults by cross-referencing their samples against the police DNA database, so helping to take serial rapists off the streets. 

The technology - also trialled in Lancashire and Nottinghamshire - will be critical in reducing delays that have plagued rape and sex assault cases as it could slash weeks off the time taken to complete forensic investigations.

It comes amid efforts by ministers, police and prosecutors to reverse the slump in rape conviction rates to a record low of just one in 50 offences - a decline attributed to delays of up to five years for victims to get justice, high drop-out rates as a result and intrusive analysis of personal phones.

Professor Fraser Sampson, the biometrics and surveillance camera commissioner for England and Wales, said early results from the fast DNA trials had been “very impressive”.

‘Impressive results’

Speaking on Policing TV, he told how he was swabbed then given his DNA profile within two hours during a visit to the Met’s forensic science labs in Lambeth, south London.

“One of the challenges is to be able to get [the results] through in time [to beat] the custody clock which is obviously ticking from the moment their detention is authorised,” he told presenter Danny Shaw.

“Usually you can’t, which means the [suspects] have to be bailed or released under investigation while that process is undertaken.”

In one case earlier this year, a man arrested in south London on suspicion of a sexual assault was DNA tested while in custody. It matched him to a historical rape, enabling police to charge him for it in addition to two current sex assaults. He is due to appear in court in July.

Without a rapid DNA test result, he would most likely have been released under investigation or bailed by police while inquiries continued into the alleged sexual assault - and before his DNA had been processed and matched.

Professor Sampson said: “The Met will be soon publishing some very impressive results [of DNA tests] while the person was still in custody for the original arrest.”

He said the technology, which brought in-house forensic science tests to the crime scene, was less intrusive than in the past when the suspect’s biometrics and fingerprints had to be sent to an outside private laboratory.

“Anything that can speed up the process, make it less intrusive for the individuals involved and make it cheaper is all the better,” said Professor Sampson.

The UK has one of the biggest DNA databases in the world with 6.7 million profiles of which 600,000 are from crime scenes. There are also 26 million fingerprints, although these are linked to a far smaller number of individuals.

Professor Sampson revealed that the biggest point of failure in capturing DNA from people in custody was the failure of police officers to seal the bag properly, which led to contamination and invalid samples.

“I'm still trying to understand why and how that keeps happening, but I'm working with police forces and the home office to understand that,” he said. It accounts for seven in 10 DNA forensic errors.

There has also been a fall in new additions to the DNA database because fewer suspects are arrested and more are questioned under caution which does not give police the same DNA swabbing powers.

“The reduction in people coming through a custody environment, particularly during the Covid 19 pandemic, has meant a corrosive reduction in the number of new prints and DNA profiles,” said Profesor Sampson.

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