BOSTON – Massachusetts announced formation Thursday of a central office to sort through the tens of thousands of criminal cases that may have been compromised by the mishandling of drug evidence at a state lab, while also broadening the investigation to determine whether problems extended beyond a single chemist.

Gov. Deval Patrick on Thursday named David Meier, a defense lawyer and former prosecutor, to head the office which will act as a “clearinghouse” for information and try to connect specific cases to drug samples tested by the chemist, Annie Dookhan, over a nine-year period at the lab formerly operated by the state Department of Public Health.

Patrick also said he has asked Attorney General Martha Coakley to conduct a separate review to determine if any problems identified at the lab could have affected the reliability of drug testing in cases other than those handled by Dookhan, who resigned in March.

Citing an ongoing criminal probe by the attorney general, state authorities have not specified what Dookhan was accused of doing or what her motive might have been.

Meier, who will be paid $12,500 per month for his services, is a partner at the Boston law firm of Todd & Weld. He spent more than 20 years as a prosecutor in Middlesex and Suffolk Counties, including 12 years as chief homicide investigator in the Suffolk District Attorney’s office.

Patrick said Meier would be an “independent and objective voice,” in the probe. Meier stressed that his role was not to act as an advocate for either prosecutors or defense attorneys, nor would he act as a judge deciding the outcome of cases.

“I stand before you today as an advocate for fairness and due process in the criminal justice system,” he told reporters.

Meier said he would begin Friday by convening a meeting of prosecutors, lawyers, representatives of the state’s trial court and agencies that could be impacted by the investigation. He said there was no timeline for the central office to conclude its work.

Patrick said his administration had not yet come up with an estimate for how much the effort will cost, but added that he would submit a future appropriation request to the Legislature. House Speaker Robert DeLeo has announced that at least two legislative committees will conduct a separate review of the crisis.

In a letter to district attorneys and the state’s public defender agency, First Assistant Attorney General Edward Bedrosian Jr. said there was no reason to believe other chemists were involved in deliberate mishandling of evidence. Coakley’s office plans to hire independent forensic experts to conduct an assessment of results.

Patrick also told reporters Thursday that he did not expect to see an “exponential” increase in tainted cases beyond the more than 60,000 drug samples involving 34,000 cases that were handled by Dookhan.

“From everything we have learned from the investigation so far, the chemist (had) her own set of rules and operated within those, and others operated within existing rules,” Patrick said.

Defendants impacted by tainted evidence would be handled on a case-by-case basis, with an emphasis on any individuals who may have been jailed unfairly. Asked if he was concerned the findings might result in the release of dangerous inmates, Patrick said his primary concern was that justice be served.

On Wednesday, a drug defendant serving time in jail was allowed to withdraw his guilty plea. David Danielli was originally charged with trafficking oxycodone pills, but he pleaded guilty to a lesser charge in June after Department of Public Health officials told prosecutors that drug samples in his case might be called into question.