Murder and rape are among the offences in 80 cases in Suffolk and Norfolk where convictions could be jeopardised due to the possible manipulation of forensic evidence.
Suffolk has a total of 28 cases involved in the current inquiry relating to Randox Testing Services in Manchester, while Norfolk has 52, police have said.
The Crown Prosecution Service and the Forensic Science Regulator now fear more than 6,000 toxicology samples nationally could have been manipulated.
This could potentially lead to miscarriages of justice in hundreds of cases.
Two men – aged 31 and 47 - at the Lancashire-based laboratory were arrested on suspicion of perverting the course of justice in February after concerns forensic tests had been tampered with.
The National Police Chiefs’ Council has said while the majority of cases affected are traffic offences, other convictions – including murder and rape cases where defendants were found guilty on evidence involving drug analysis – could be overturned.
It is not known how many of the Suffolk and Norfolk cases have already resulted in convictions or are still awaiting their conclusion.
Detective Chief Superintendent David Skevington said: “Suffolk and Norfolk were originally notified of eight cases which were affected by the issues involving sub-contraction of toxicology testing to Randox Testing Services, with more recent events increasing this number to 80.
“This includes 52 in Norfolk and 28 in Suffolk, with investigations ranging from murder to rape and drug driving offences.
“The manipulation of forensics the national inquiry has uncovered has resulted in an extremely serious impact on the criminal justice system.
“Both Forces are doing everything they can, as quickly as they can, to identify cases where there could have been miscarriages of justice as a result.
“The constabularies 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. Police and the CPS will make contact with any affected members of the public in due course.”
In February Randox Testing Services said it was treating the matter with the “utmost seriousness”.
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