A pair of scandals at two state labs that process evidence in drug crimes has led to thousands of cases being dismissed. Middlesex County District Attorney Marian Ryan said she's worried that thousands more cases might be in jeopardy. Ryan contends that the Massachusetts Inspector General may not have gone far enough in investigating former state chemist Sonja Farak, who pleaded guilty to stealing drugs from the lab in 2014. The inspector general and the state's secretary of public safety are pushing back. Ryan spoke with GBH All Things Considered host Arun Rath. This transcript has been edited for clarity.

Arun Rath: Farak is the chemist who worked out of a lab in Amherst who ended up serving time in prison for using drugs on the job that she was supposed to be testing, drugs that were evidence in criminal cases. In a letter you sent to the Baker administration late last month, you said that while her conduct at the Amherst lab was investigated, her previous work at the Hinton lab in Jamaica Plain was not fully examined. Can you talk about that?

District Attorney Marian Ryan: Sure. So Farak initially worked out of the Hinton lab, and obviously worked on lots and lots of cases. At some point she transferred out to the Amherst lab. So in the meantime, also working at the lab was the chemist Annie Dookhan. The inspector general did an investigation around the Dookhan issue, during which there were some concerning issues that arose with respect to Farak. The inspector general in their initial report said that Dookhan was the only "bad actor" at that lab.

In the meantime, all of this new information came to light about Farak's work out in Amherst, which coupled with some of the flags that had arisen in the investigation, as well as the later behavior in some of the testimony that came out in the cases in the Western part of the state, gives rise to that concern that there should have been a more complete look at what, if anything, might have happened while Farak was working at Hinton.

Rath: Annie Dookhan was a state chemist who also served time in prison. She tampered with evidence in drug cases, and her misconduct also led to thousands of cases being dismissed. At one point, an official with the FBI told the inspector general there were at least seven chemists working at the Hinton lab who merited investigation.

Ryan: Yes. One of which was Farak.

Rath: Does that mean there were five others?

Ryan: Six others, I guess. Because it was in addition to Dookhan. My understanding is that it was Dookhan plus seven. One of the seven was Farak.

Rath: So this is among the reasons you're saying that there is more to be looked into here.

Ryan: Yes. We are prosecuting people on the basis of the evidence that we present, among other places, coming from the lab. It's critical for us that we can rely on the evidence that we are presenting. It's important for the people both being prosecuted and the public that they can have confidence in the integrity of that prosecution.

The question has continued to be raised over the six or seven years now that this has been an issue as to, given what we now know as a result of the hearing out in Western Massachusetts about Farak's own drug use, whether that began before she came to work for the Commonwealth, and whether it's reasonable to assume that that drug use may have impacted her work at Hinton as it did at Amherst a few years later.

Rath: The state's Inspector General Glenn Cunha, and the state's Secretary of Public Safety Thomas Turco are pushing back against your letter. They say that you are exaggerating the fallout from the Farak case for effect. Could you respond to that?

Ryan: Well, those numbers that we're quoting are the numbers that were provided to us by the Massachusetts attorney general's office as the number of cases that they worked on. But the reality is that that is to some extent a red herring, because if the integrity of one person's conviction is in jeopardy, that's too many.

Rath: Can you explain the timing of this letter? why now?

Ryan: Because as a result of litigation in the Superior Court here, we are not going to proceed on the Sutton case, which is one of the cases before us. But we have a number of other cases. It is not as though the Sutton case being disposed of is going to resolve this issue. This issue has been around now for several years. We have many other cases in Middlesex County, there are other cases across the state, where people are legitimately raising this issue.

It just needs to be resolved one way or the other. Either there is enough information that the inspector general has that they can definitively say whatever the conduct was of Farak, or further investigation needs to be done about the years of her employment at Hinton.

Rath: Farak was charged and served time in prison for her misconduct at the Amherst lab. If a new investigation would reveal misconduct at the Hinton lab in Jamaica Plain, could she face charges again? Could others potentially face charges, depending on what emerges?

Ryan: I can't speak to that, because I don't know. Obviously you can't speculate about what might come up. I don't know the exact timing. I don't know whether there would be statute of limitation questions. I just don't know that.

Rath: Before we let you go, I've got to ask you: there's a push underway right now across the country for more accountability in the criminal justice system. Do you see this case in the context of that at all?

Ryan: Yes, I do. People have a right to know how evidence is produced and to be able to feel that it passes that test of being sufficiently trustworthy to be used to convict people. This is the kind of evidence that can be used to gain a conviction against someone, to send someone to jail. When we're doing that level of serious work, people certainly have a right to expect that the evidence we're using to do that is of the highest quality.

The Office of the Inspector General provided GBH News with a copy of its reply to Ryan's letter to the Baker Administration, saying that its investigation into the Hinton lab in Jamaica Plain did not find evidence that Farak or any other chemist at the lab besides Annie Dookhan was engaged in misconduct in evidence testing. The Inspector General's office stated that a further response to Ryan's letter, with additional information about its investigation, will be forthcoming.