More than 6,000 forensic tests used to secure criminal convictions feared tampered with

Forensic tests on more than 6,000 toxicology samples including some used to secure rape and murder convictions are feared to have been tampered with and are no longer considered to be reliable.

Two men have been arrested by Greater Manchester Police over claims that hundreds of criminal cases were mishandled by the Randox Testing Services (RTS).

At first it was believed that 484 cases had been affected, but the number now under the spotlight is feared to be greater than 6,000.

It has sparked concerns that scores of convictions, including for rapes and murders, could be overturned.

Many of the affected cases related to Road Traffic Act offences. Credit: PA

Since the emergence, the National Police Chiefs' Council has insisted around 90% of the affected samples can be retested.

A team of forensic experts are currently identifying any live cases which require retesting and past cases where convictions could be unsafe, the NPCC added.

"The majority of cases affected are Road Traffic Act offences such as drug driving," an NPCC spokesperson said.

"However, RTS provided toxicology tests for other offences including rape, assault and murder so it is possible these cases could be affected."

Hundreds of criminal convictions could theoretically be overturned. Credit: PA

The allegations came to light in January, and involve alleged manipulation of data during tests.

The two men arrested at an RTS Manchester laboratory on suspicion of perverting the course of justice were aged 47 and 31.

NPCC forensic expert Deputy Chief Constable James Vaughan described the tampering as a "serious breach" of "very rigorous professional standards".

"We now have a clearer picture of the scale of this data manipulation and have been able to set out a plan of action in partnership with RTS, the Forensic Science Regulator and the CPS," he said.

"The numbers affected could change as our investigations progress.

"We are prioritising the most serious and pressing cases but all cases where there could have been an impact on prosecution will be assessed, retested and appropriate action taken."

A spokesman for RTS said they were fully supporting the police investigation and are coordinating retests of the affected samples at an external lab.