Now, it turns out that a prominent law firm whose lawyers often appear in Boston courts paid for Dougan’s ­defense, giving him at least $85,000 worth of free services – and perhaps much more – from one of the most prestigious legal teams in the city.

The pro bono legal services provided by the Boston law firm Foley Hoag could violate the rules of ­judicial conduct that prohibit judges from receiv­ing gifts from law firms whose attorneys have ­appeared before them or are likely to in the future. State ethics law also bars public officials from accept­ing most gifts.

The free legal services, confirmed by Dougan in mandatory reports to the Supreme Judicial Court and the State Ethics Commission, are certainly unusual. Michael Mone Sr., a leading Boston lawyer who frequently represents judges before the Commission on Judicial Conduct, said he ­always sends them a bill, ­because he believes he must.

“My interpretation of the law is that in representing individual judges, you cannot make that a gift,” Mone said.

Dougan declined to comment, but his lead attorney, Michael B. Keating of Foley Hoag, argued that no rules were broken. Keating said he was simply standing up for judicial independence.

“As a private lawyer, I decide how much to charge my clients,” Keating said in an e-mailed statement. “Over the years, I have done a great deal of legal work pro bono or at reduced rates. That work has ­included conducting investigations of judges, without compensation, as special counsel to the Judicial Conduct Commission.’’

He said the arrangement with Dougan violated no ethics rules, because neither he nor any of the lawyers who worked on the case have ever appeared before Dougan specifically. However, numerous Foley Hoag lawyers make appearances in district courts, including Boston Municipal Court, where Dougan is the first justice of the downtown division.

Jill Pearson, the former executive director of the Commission on Judicial Conduct, said the rules are clear: Judges cannot get free lawyers to represent them in misconduct investigations.

“The judge pays his lawyer his full, usual fee,” said Pearson, who retired last August while her agency was still conducting its two-year investigation of Dougan. “It would be misconduct for a judge to pay any less, as that would constitute an improper gift from the lawyer to the judge,” she added, stressing that she was speaking generally and not about Dougan specifically.

Suffolk District Attorney Daniel F. Conley triggered the investigation in December 2010 when he took the unusual step of filing a formal complaint about Dougan’s alleged bias. The lengthy report, filed with the Judicial Conduct Commission, detailed dozens of cases in which Dougan sided with defend­ants despite what Conley said was convincing evidence of their guilt.

A Globe report on the controversy found that Dougan’s reputation for favoring the defense had even spawned a nickname from one criminal defendant: “Judge Let Me Go.” The Globe found that Dougan’s rulings were reversed or modified on appeal more often than any other Boston Municipal Court judge.

But judges and defense attorneys rushed to the defense of Dougan, accusing prosecutors of attempting to bully an independent-minded judge.

Keating, who is chairman of Foley Hoag’s litigation department and a former head of the Boston Bar Association, said that he took the case because there was “an important principle at stake.”

“I have often represented individuals, without regard for ability to pay, when I believed that a lawyer could make a difference in vindicating important principles,” he said. “In this case, that principle is ­judicial independence.”

Keating and two colleagues represented Dougan for free throughout the investigation, beginning in 2010 and continuing until at least Nov. 27, 2012, when they responded to a legal filing from Conley’s office. Along the way, they argued and won a landmark ruling from the Supreme Judicial Court preventing investigators from asking Dougan how he arrived at his decisions.