More than 40 motorists have been wrongly convicted of drug-driving after evidence was re-examined following alleged drug test tampering at a scandal-hit lab.

The drivers were banned from the road and in some cases fined, but after the review their convictions have since been overturned.

In what is Britain's biggest ever forensics scandal, it was revealed a further 50 cases have also been dropped due to alleged tampering by rogue forensic scientists.

Around 10,500 test results are being re-analysed after data was allegedly manipulated by rogue scientists at Randox Testing Services (RTS) in Manchester.

The unprecedented operation began in January 2017 and is likely to continue until the end of 2019. Randox estimates it will cost the firm £2.5million to have the samples re-tested by other laboratories.

The drug-driving figures were revealed today by the National Police Chiefs' Council (NPCC), which described it as a 'most serious breach' of forensic science standards.

Hexagon Tower in North Manchester in which the labs of Randox Testing Services ( RTS ) Manchester are based and where an investigation is underway into 'manipulated data'

Of the 10,500 cases under review, 275 are understood to be murders, 1,000 are sex cases - including rape.

Another 150 involve deaths on the road, 500 concern sudden death, but 7,500 concern drug-driving.

The scandal has raised fears that innocent people could have been jailed after being falsely convicted for serious crimes, including rape and murder.

Three scientists were arrested at RTS when it was hit with the allegations last year.

Experts are now reviewing blood tests that it is feared may have been doctored by employees at RTS.

The NPCC said more than 50 further drug-driving investigations were dropped before prosecutions were won, with this number likely to rise.

Forty-one drug-driving cases which had already resulted in convictions or guilty pleas have since been reopened and overturned.

The retesting of cases opened since 2014 came after allegations emerged that scientists at a Randox Testing Services (RTS) site in Manchester had manipulated forensics data.

The laboratory worker has been questioned by detectives investigating the potential doctoring of more than 10,000 blood sample results [file photo]

The results of the investigation were described as a 'national scandal' with a 'devastating impact' by a lawyer seeking damages for 35 of the 40.

'People have lost their driving licences, and as a result lost their employment, struggled to pay bills such as mortgages and rents, and some have been unable to travel to see their families and children,' added Andrew Petherbridge, of Hudgell Solicitors.

One of those is Luke Pearson, a scaffolder from Manchester who lost his job when he accepted a 12-month driving ban and a fine before having his case overturned in February, according to the firm.

Manchester lab at centre of storm Business had been booming at Randox Testing Services as a result of a Government crackdown on drug-driving. Scientists at its Manchester laboratory worked with the Home Office to develop sophisticated blood and urine tests needed to establish if motorists had been taking illegal substances such as cocaine and cannabis. A new law, introduced in March 2015, meant anyone who tested positive for one of 16 specified drugs could be prosecuted rather than police having to prove they were unfit to drive. RTS, part of Northern Ireland-based health giant Randox, was contracted by police forces to analyse samples taken from suspects by officers. Thousands of the tests were sent to the firm’s lab at the Hexagon Tower in Blackley. But in January this year, RTS began an internal investigation when bosses suspected a ‘rogue operator’ had been manipulating quality control data needed to double-check a test result. RTS dismissed one employee and suspended another, and both were arrested at home and questioned on suspicion of perverting the course of justice. All suspect tests had to be re-checked and RTS was stripped of its Home Office accreditation while investigations were carried out by the forensics watchdog as well as police. The criminal investigation has now widened to include five other people recently questioned under caution. However, no one has yet worked out what the possible motivation could be. RTS described the events as ‘bizarre’ and said that it ‘truly regrets the fact a rogue operator or operators existed in RTS Manchester’. Advertisement

'I think it is disgusting that this has been able to happen to so many people, and it was devastating to me,' the 26-year-old said.

'It all put a strain on life, and on my relationship with my girlfriend as I was the main earner and we struggled with bills and rent.

'I was only an occasional, light cannabis user, but when the police tell you that science says you are guilty you can’t argue.'

The re-investigation of cases since 2014 was launched in January last year after allegations emerged that scientists had manipulated forensics data at an RTS site in Manchester.

Two men, aged 31 and 47, were arrested on suspicion of perverting the course of justice by Greater Manchester Police and have been bailed until January.

Six more people have been interviewed under police caution with one remaining under investigation.

The laboratory was used by 42 of the UK’s 43 forces.

The investigation has found around 3 per cent of cases re-analysed have been dropped or overturned. All of these were brought over drug-driving allegations.

A further case referred to the appeals court saw a sentenced reduced, one appeal unsuccessful with a fourth pending, Mr Vaughan said.

He believes the botched results are due to the manipulation of test results rather than samples being tampered with – but was unable to guarantee samples’ fidelity at this stage.

'We can’t be fully sure, that’s part of the investigation into Randox,' he said.

Of the 40 cases reopened, they were all dropped using powers under the Magistrates’ Courts Act.

All had received driving bans or fines but had not been sent to prison, Mr Vaughan said.

Retesting is expected to continue into December 2019 and has been slower than expected partly due to an existing shortage of forensic testers which has been exacerbated by the scandal.

He added: 'We have a perfect storm of a chronically saturated market, now you have one less accredited provider in the market and now you have 10,500 new cases for retesting.'

More than 10 per cent of the most serious cases still must be retested, with thousands still needing fresh analysis.