DNA contamination blamed on human error

A Home Office statement said an investigation by the Forensic Science Regulator Andrew Rennison is still looking at whether other cases are also at risk but so far 26,000 other samples have been checked and no more have been identified.

The error occurred at what is described as the most advanced automated DNA testing system in the UK at LGC forensics labs in Teddington. A used plastic sample holder containing up to eight vials of DNA was mistakenly reloaded into the machine by a laboratory worker, instead of being put into a bin. The system had been installed in March 2011, and the contamination occurred in October.

Every DNA sample in that seven month period has been checked, and LGC said no other instance of contamination had been uncovered. The regulator is now working with the company in monitoring new procedures that have been put in place, to ensure the mistake is not repeated.

LGC told Channel 4 News: “LGC’s investigation into this incident has been independently audited by United Kingdom Accreditation Service (UKAS). The audit confirmed LGC’s own analysis of what happened and confirmed that past cases have now been thoroughly checked to ensure that this did not happen anywhere else. A number of changes have been made to the system to make the distinction between new and used labware even clearer than it was previously.”

The DNA mix up was discovered by Greater Manchester Police detectives, after they had charged a 20 year old suspect in October last year with raping a woman in a park.

At that time LGC had informed the GMP that there was a strong match with DNA extracted from clothing. But detectives found that the suspect could not have been at the scene, because he was in prison 300 miles away, awaiting trial on other unrelated offences.

Greater Manchester Police were informed of the mix-up in March, and the Crown Prosecution Service dropped the case against Adam Scott from Exeter, in Devon.

There was some concern that the blunder could have implications for the convictions in the Stephen Lawrence case, which depended heavily on DNA evidence, and for which some of the tests were carried out at the same laboratory, but further tests to double check results were carried elsewhere.

Simon Israel is the Home Affairs Correspondent for Channel 4 News