At least 129 cold cases – including violent crimes, sexual offences and sudden deaths – are being re-examined by police following concerns about forensic toxicology tests.
The cases, which cover Beds, Cambs and Herts, have been highlighted after allegations emerged about tests carried out by a private firm.
This includes 60 cases and 107 samples in Hertfordshire, between 2013-17.
Superintendent Russ Waterston said: “These cover a wide variety of offences. The majority relate to road traffic offences. In line with the national response, the most urgent cases, including those that are currently going through the criminal justice system, are being given retesting priority.
“To date 22 samples have been re-tested and the results have remained unchanged. As we progress with this review we will of course ensure that contact is made via the Crown Prosecution Service with anyone who has been affected by inaccurate samples.
“Understandably, this news will cause concern but I would like to reassure the public that it is very unusual that one single strand of evidence, such as toxicology results, would form the entire basis of a case.”