The Nassau County District Attorney wants a special prosecutor to investigate possible wrongdoing at a now-closed crime lab.
DA Kathleen Rice says she will ask for court approval to appoint Eric Dinallo, the state's former insurance superintendent, to lead the probe.
Errors in drug and other forensic tests, potentially affecting scores of criminal cases, forced the closure of the crime lab last week.
However police supervisors may have been aware since September that errors were occurring with the analysis of drug evidence, officials said.
The lab mistakes could lead to exoneration or a reduction in charges for some people convicted of drug offenses, officials said.
A national accrediting agency had placed the lab on probation in December.