The Suffolk County district attorney refused two years ago to prosecute Boston Public Library janitors for collecting overtime for hours they didn’t work because the DA said library officials had known about the scheme for years and let it continue, according to newly uncovered records.

WGBH News' New England Center for Investigative Reporting first reported in 2018 that library custodians were routinely paid full eight-hour overtime shifts for cleaning up after private events at the central library, even if they only worked a few hours.

In a 2018 email to the Boston Police Department, Assistant Suffolk DA Teniola Adeyemi said the office would not press charges for alleged overtime theft because “all the evidence points to a general understanding between janitors and supervisors that if they signed up for the ‘event clean-up,’ then they would receive the full eight hours pay even if they did not work the full eight hours, provided that the library was cleaned before they left.”

The email was recently obtained by WGBH News through a public records request after a long battle with the Boston Police Department, which repeatedly claimed that no records existed regarding the investigation. (Disclosure: WGBH has a broadcast studio inside the central library.)

The overtime investigation “was an embarrassing set of events,” library President David Leonard said in an interview last week. “I feel responsible for what happened, but I don’t believe I would handle it any differently if we had to do it over again.”

The library charges thousands of dollars for patrons to rent out its elegant spaces for private after-hours events such as weddings, holiday parties and meetings. This requires janitors to work overtime hours to clean up afterward. It had been standard practice for years, however, for the cleaning crew to get paid for a full eight-hour shift even if the work was completed sooner and they took off early, which was frequently the case.

In 2018, at the request of BPL officials, the police department investigated the actions of the janitors and then turned the results over to the interim Suffolk County DA at the time, John Pappas, for possible criminal prosecution. But the DA’s office wound up scolding the library, concluding that prosecution would be a waste of time and money because key BPL executives had been aware of the overtime practice for years, but did nothing about it, thus making for a weak legal case.

Adeyemi noted in the 2018 email that there was no reliable way to prove that the janitors did not remain in the building for the full eight-hour shift. She also said for most of the janitors, the disputed amount would be less than $1,200. And she said there was no allegation that the library was not cleaned.

Adeyemi wrote that Michael Durfee, the manager of central library custodians, said that throughout his years of employment, it was common practice for the custodians to leave when they had completed their work.

Durfee’s colleague, Ralph Henry, the manager of library buildings, told Adeyemi that there was no oversight to ensure the accuracy of the janitors’ timesheets and that he signed them fully recognizing that they would leave after they completed their work, regardless of how many hours they worked. The timesheets were submitted and approved before the overtime shifts began, Adeyemi said.

Adeyemi also argued that the City of Boston lost money as part of the private events, because the janitors' wages were paid out of the city payroll, not out of user fees paid to the library. Leonard, the BPL president, takes issue with that, claiming that the library reimbursed the city for the payroll expense.

Although Adeyemi concluded that “the overnight janitors should not be faulted for following a system that has long been the norm,” at least one of them — Calogero Russo — was fired.

Russo told WGBH News in 2018 that he struggled with addiction, and was called into a disciplinary meeting after showing up to work under the influence of drugs. It was at that time, he said, that he was accused of falsifying his timesheet and he “kind of let the cat out of the bag” about janitors leaving early but being paid for the full shift.

Russo said many other janitors were doing what he did, but BPL spokeswoman Lisa Pollack this week refused to say whether any other janitors were let go.

The janitors’ bosses — Henry, Durfee, and a third BPL facility official, James Meade — were terminated. The Boston Guardian reported last year that Henry received a settlement of $34,000 after having exhibited remorse for his involvement. Durfee and Meade did not get any settlements, according to Pollack. Henry and Durfee could not be reached for comment.

Last year Meade’s lawyer, Joseph Cacase, told WGBH News that his client had no knowledge of the alleged overtime theft. “Mr. Meade had nothing to do with any alleged wrongdoing,” he said. “Mr. Meade did not participate in it. He did not approve it.”

Adeyemi, the assistant DA, wrote that the library should put policies in place to avoid misreported overtime. “If Boston Public Library does not wish for this to continue, they should set clear guidelines regarding overtime and review and check the timesheets after each shift before they are approved,” she wrote.

Leonard said that such procedures have been put in place to prevent the imbroglio from happening again.

“We took the appropriate action and now we want to put all of it behind us,” he said. “We want to ensure that people continue to view the Boston Public Library as a trusted institution not just in terms of how they consume our services, but how we conduct ourselves operationally.”

Colman M. Herman is a Boston-based freelance reporter.