More than 40 criminal convictions for driving offences have been quashed following an investigation into alleged 'data manipulation' at a Manchester forensic drug testing laboratory.

Samples from driving offence cases were handled on behalf of police forces across the country by private firm Randox Testing Services Laboratory, based in Blackley, north Manchester.

Allegations that scientists based at the lab had manipulated data concerned with sample analysis led to re-testing in some 10,500 separate cases.

At a briefing in London on Thursday, the National Police Chiefs' Council (NPCC) gave an update on the investigation.

It emerged two men, aged 31 and 47, have been arrested on suspicion of perverting the course of justice by GMP in connection with the enquiry and were released on bail pending further investigation until January.

Six more people, two women and four men, have been interviewed under police caution, although only one remains under investigation, the police chiefs council said.

Ongoing investigations into suspected drug-driving offences have also been halted by police as a result.

The NPCC's forensics lead, Chief Constable James Vaughan, said more than 50 drug-driving investigations had been dropped after some 2,700 cases were re-analysed so far.

(Image: Daily Record)

A further 41 people who had already been convicted of drug-driving offences, or had pleaded guilty, have since had their cases reopened and overturned, he added.

The retesting of more than 10,500 cases opened since 2014 came after the allegations surrounding Randox first emerged.

The major investigation into the lab, which was used by 42 of the UK's 43 forces, was launched in January 2017.

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Scores of court cases will now need to be reviewed by the Crown Prosecution Service to see if they were affected by 'compromised data'.

It emerged in November 2017 that police forces had suspended all contracts with the firm.

Chief Constable Vaughan said: "The integrity of forensic science is a fundamental part of our criminal justice system and we are working tirelessly to minimise the impact of this serious breach of standards.

"Managing the process for retesting over 10,500 potentially affected cases has been a major national police operation. We will continue this process until we can assure the public that we have retested samples in every case where it is necessary and possible.

"We’ve retested nearly 90 per cent of the highest priority cases. Of the cases retested three per cent have resulted in different outcome and a further four cases referred to the Court of Appeal - these are all road traffic cases.

"Unfortunately, the retesting process has been slower than we had either hoped or anticipated, as a result of the limited specialist and independent capacity within the forensic marketplace."

(Image: National Police Chiefs Council)

The alleged manipulation came to light when Randox Testing Services, during an internal investigation, uncovered irregularities and reported the details to GMP. The criminal investigation was subsequently launched.

Of the 10,500 cases identified, nearly 4000 have been retested or submitted for retesting and 2300 cases have been struck from the retesting process as they have been deemed unlikely to result in a change to the criminal justice outcome, police said.

In a statement GMP said: "Greater Manchester Police are continuing a criminal investigation into forensic results issued by Randox Testing Services (RTS). Our investigation concerns the manipulation of data concerned with sample analysis. We do not have any information or evidence to suggest that the physical samples have been directly tampered with."