Rogue forensic workers feared to have doctored the results of 500 lab tests - throwing hundreds of court cases into doubt

Almost 500 criminal investigations are being reviewed after test results at a forensics lab were allegedly tampered with by two "rogue" scientists.

Two men have been arrested on suspicion of perverting the course of justice after a major security breach was uncovered at the Randox Testing Services (RTS) lab in Manchester.

The laboratory, which carries out toxicology tests for police forces across the country, has identified a total of 484 cases which may have been compromised.

Much of the work carried out at the laboratory involves the analysis of blood samples of people arrested for allegedly driving while under the influence of drugs.

The security breach raises the prospect that hundreds of people could have the victims of miscarriages of justice and the Home Office and Crown Prosecution Service have been made aware of the case.

The laboratory also carries out a small number of toxicology tests in pathology cases, to establish if drugs played a part in a person’s death, but it is not clear if any of those tests are among those affected.

One of the two men arrested by Greater Manchester Police has been dismissed by the company, but it is not clear what the alleged motive may have been.

It is understood that while samples themselves were not tampered with, the data against which they were measured was manipulated, meaning the accuracy of the tests could not be guaranteed.

Detectives are now working to establish if the alleged manipulation was the result of staff trying to cut corners or whether the motive was more malicious.

A source at the company said the staff did not have to meet performance targets in relation to the tests, so it was unlikely they were trying to improve their own performance through data manipulation.

A spokesman for RTS said the issue came to light when an "anomaly" was spotted in the data in January and an internal investigation was launched immediately.

The police were then called in and two members of staff, aged 47 and 31, who had worked at RTS for three years, were arrested.

Dorset Chief Constable Debbie Simpson, who is the National Police Chief’s Council lead for forensic science, said: "We have been made aware of a quality failure with Randox Testing Services (RTS) which is currently being investigated and a criminal inquiry has been launched by Greater Manchester Police.

"Randox has provided each force with a list of cases that could have been affected. Working in partnership with the Crown Prosecution Service, we have provided guidance to forces so they are able to review each case to determine if compromised data played a part in prosecution and the CPS will then take appropriate action in any cases identified."

A spokesman for GMP confirmed it had been asked to investigate "forensic results issued by Randox Testing Services".

The spokesman added: "Randox Testing Services have provided forensic services to police forces, including GMP, for the past two years. The organisation is being fully co-operative (with) the investigation."