DNA database under fire after samples mix-up

By Jason Benetto Crime Correspondent

THE WORLD'S first DNA database - hailed by the Home Secretary and police chiefs as one of the biggest breakthroughs in crime-fighting this century - is mismatching samples from innocent people and has had problems with contaminated products.

Confidential documents obtained from the DNA database headquarters in Birmingham reveal that there have been at least three cases in which the genetic profile of a suspect has been wrongly matched to DNA taken from the scene of a crime such as rape or murder.

In one incident last month two DNA samples were said to be identical, yet forensic scientists noticed that one was from a 14-year-old girl from Merseyside and the other was from a 21-year-old man from Lancashire.

The Forensic Science Service, the government agency responsible for processing DNA samples, stressed that in all of the cases uncovered the mistakes were discovered during further routine testing. The FSS argues that the system for checking is foolproof and that no mismatches could reach court. Police and lawyers frequently cite the chances of a mismatch at 40 million to one.

Nevertheless, the disclosure that mismatches and contamination are taking place adds to the disquiet expressed by some lawyers and civil-rights groups that courts are relying too heavily on a technique that has yet to be proved to be entirely reliable.

The national computer DNA database started in April. Police can take samples such as hair and saliva from anyone charged with a recordable offence - one that carries a possible prison sentence. Scientists compare DNA samples, such as blood and semen, taken from crime scenes with the DNA of suspects. About 135,000 samples from people accused of burglary, assault and sexual offences were hoped to be taken in the first year. Up to five million records are expected to be held on the system eventually. So far about 11,000 profiles have been completed out of 70,000 samples taken. There have been 45 confirmed matches.

The three unconfirmed matches were obtained by the TVF production company and are shown in tonight's Equinox programme, DNA in the Dock (C4, 7pm).

The mismatch involving the girl and man was caused by a technician mixing up two test tubes. Instead of analysing two different DNA samples, he examined the same person twice but recorded it as two separate people. Two other errors occurred when bar codes used to identify suspects became corrupted and incorrectly linked suspects with crimes.

Dr David Werrett, the director of service development at the FSS, denied there had been any difficulties with contamination.

However, a notice written by him in April under the headline "Contamination" talks about a "serious breach of professional conduct" at the Birmingham laboratories in which dirty gel from the fourth floor contaminated DNA samples on the fifth floor.

Dr Peter Gill, head of biological science research at the FSS, said yesterday: "Contamination does occur on rare occasions, but our procedures are designed to pick up any problems and prevent them from affecting the final results."

He said that before a "match" is confirmed it is tested a second time, then a new sample is taken and sent to a separate laboratory for further analysis.