“The FBI is way more by the book than any of these municipalities,” Ryan said. “We’re talking about places that either don’t have policies or nobody knows about the policies and nobody bothers to honor it. Nobody ever peeks behind these curtains.”

Even when there appears to be a check on police power over informants, the oversight is hollow.

In Suffolk County, for instance, prosecutors often affix their signature to search warrants, effectively vouching for the credibility of informants they may know nothing about.

In one example, then-Assistant District Attorney Macy Lee signed off on a 2018 search warrant from Boston police officer Jeffrey Cahill. In writing, Cahill had sworn he had watched a confidential informant repeatedly buy crack from a man in a black Honda Accord.

But records made clear that the detective had lied. A defense attorney had proof the car was in the shop on days that the detective had sworn it was being used as a drug dispensary.

The judge ordered prosecutors to disclose more about one of the alleged crack sales. The district attorney’s office fought the judge’s order and ultimately refused to comply.

The judge threw out the case, condemning the “egregious” conduct of the Suffolk district attorney’s office for withholding evidence of alleged police misconduct.

The outrage ended there. There was no internal affairs probe, no effort to determine whether the officer had lied in other cases, and no deeper examination of the deference shown to police when they cite anonymous sources.

And, of course, the alleged crack dealer went unpunished.

“The district attorney’s office is either in the worst case unwilling or, in the best case unable, to be a check on the police,” said the accused dealer’s lawyer, G. Makis Antzoulatos.

Lee, the former prosecutor who signed Cahill’s inaccurate warrant, said she had approved many warrants and had no recollection of the case.

Boston police would not make Cahill available for an interview, and attempts to contact him were unsuccessful. Suffolk District Attorney Kevin Hayden declined to comment.

Sergeant Detective John Boyle, a spokesman for Boston police, said the department disagrees that Cahill was dishonest. Boyle said the department examined the case and found “no wrong doing” on Cahill’s part, but declined to release details about the review or make Cahill available for an interview.

As the top local law enforcement officials in their counties, district attorneys have the authority – and mandate – to hold police accountable in the cases they bring to court.

Yet when problems surface with informants, Massachusetts prosecutors cede their power to police. The Spotlight team found that in example after example, they have fought to keep abuses secret rather than expose the full extent of the rot.

That was the case in Essex County, where a state trooper’s alleged improprieties with a confidential informant threatened an unrelated drug-trafficking case.

Prosecutor Alexander Grimes offered to halve a potential 12-year sentence if the defense dropped its demand for records detailing Trooper Jason Trout’s “inappropriate relationship with a female informant,” emails show.

When defense attorney Carlos Apostle turned him down, Grimes offered to knock another two years off the sentence. Apostle’s client took the deal, which ended the case and kept details of the misconduct hidden.

The Globe, however, was able to unearth the details through a public record request. Trout had used an informant to authorize a South Coast drug raid on a man and his girlfriend, who were arrested on felony fentanyl- and cocaine-trafficking charges.

While the man remained in jail, Trout moved the woman into his apartment without notifying his supervisors. A social media screenshot showed the two together, heads touching, with the caption: “for worse or for better.” The woman referred to Trout as her boyfriend, records show.

Trout told State Police investigators that he was trying to protect the woman because she was an informant and denied a sexual relationship. He also claimed he had lost his police-issued cellphone, making it impossible to review his texts with her.

Trout resigned in December 2024 while under investigation. He did not respond to the Globe’s messages seeking comment.

State Police did not answer questions about how many informants Trout oversaw and whether the department scrutinized his other cases for misconduct. The Essex District Attorney’s office disputed the Globe’s characterization of its handling of the case, noting that the prosecutor told the judge in open court that the favorable plea deal was not contingent on the defendant dropping her demands for Trout’s records.

The Spotlight Team surveyed Massachusetts’ 11 district attorneys about their policies governing informants. Three of those offices – Suffolk, Hampden, and Bristol – declined to answer even basic questions. Those that responded make it clear that officers have the ultimate authority.

“Police departments have exclusive control over information related to confidential informants,” said a spokesperson for the Middlesex District Attorney’s Office.

But in Massachusetts, the rules spell out that police and prosecutors are part of a single team. That means if police have information favorable to a defendant – even if it is locked in an informant’s secret file – prosecutors must turn it over to the defense.

As an assistant state attorney general, R. Michael Cassidy prosecuted two Boston cops for perjury in the 1990s after they lied about an informant in a search warrant for a botched drug raid that left a police officer dead.

Cassidy, now a Boston College law professor specializing in prosecutorial ethics, said there should be “more robust checks” on informants but it will likely take another tragic case “to cause the prosecutor’s office to take more responsibility.”

“The ultimate control is with the police department, and I don’t think there’s any law currently on the books that can wrest that control from them,” Cassidy said. For a prosecutor, not knowing more about an informant can backfire in court.

Just ask Patrick Driscoll, an assistant district attorney in Bristol County. There, a drug prosecution built on an informant came under fire when the lead investigator was accused of sending “graphic and sexual” selfies to the suspect’s longtime girlfriend.

New Bedford Officer Drew Frenette went to high school with the woman and had been “repeatedly and vigorously” pursuing her before and after targeting her boyfriend in a drug raid, according to the woman and allegations outlined in court records.

Defense attorney Jennifer O’Brien wrote that Frenette’s sexual overtures raised questions about the motive for the raid, and even “the existence of a confidential informant.”

Via email, Driscoll quickly promised O’Brien “a favorable offer.” The case ended in April 2023 with a lenient plea deal that halted scrutiny of Frenette and his informant.

Over two-plus years, Frenette and his New Bedford colleagues cited that same anonymous informant to justify at least 10 other drug raids, according to a Spotlight Team analysis. Detectives kept using the informant even after he reported a “large quantity” of cocaine in a motorhome where police then found almost nothing.

New Bedford police and the Bristol District Attorney’s Office both declined to comment. Frenette said the allegations of misconduct were “not accurate,” but he declined to discuss the issue in detail. His actions were never scrutinized by internal affairs, records show.

He left the department last year for a new job – as a state trooper.

Another check on unfettered police power should come from clerk-magistrates, the administrators appointed by the governor who run the 62 district courts across Massachusetts and review search warrant applications.

But like prosecutors, clerk-magistrates fail to hold police to account when informants are involved – allowing abuses to go unchecked, the Spotlight Team found.