The Massachusetts Senate turned over a trove of records, including e-mails, to a federal grand jury earlier this year amid a US attorney’s investigation into Bryon Hefner and his relationship with his husband, Senator Stanley C. Rosenberg, according to court documents.
Senate attorneys disclosed the probe’s existence as part of documents they submitted in a separate state criminal case against Hefner, in which the chamber is fighting a request from Attorney General Maura T. Healey’s office to obtain interviews from the Senate’s own investigation into Rosenberg.
The filing does not indicate whether the federal investigation is still ongoing, and Anthony E. Fuller — an attorney with the Senate-hired firm, Hogan Lovells US LLP — said the firm “did not share any substantive information” about its investigation with either the US Attorney or the attorney general’s office.
The filing, however, marks the first public acknowledgment that Hefner’s alleged behaviors had drawn the attention of federal authorities.
A spokeswoman for the US attorney’s office did not respond to requests for comment.
Fuller wrote that after the Senate hired his firm in December, attorneys immediately became aware of investigations by both Healey’s office and the US attorney “concerning Mr. Hefner and his relationship to Senator Rosenberg.”
The Globe, citing information from people familiar with the inquiry, reported in December that the FBI had begun looking into allegations that Hefner had assaulted several men. At the time, agents were interested in whether Hefner offered a quid pro quo to his alleged victims, using his relationship with Rosenberg — then the Senate president — to influence the chamber’s business in return for sexual favors. Federal authorities have not filed any charges against Hefner or Rosenberg.
Months later, both state and federal prosecutors issued subpoenas to the Senate — the attorney general on Jan. 30 and the US attorney on Feb. 8 — “seeking the very same e-mails and other records which we were utilizing to conduct our investigation,” according to Fuller.
He said the Senate complied with that initial request, but that the firm did not share any additional information with prosecutors.
“The only communications shared between Hogan Lovells and the government concerned the timing of when our investigation might be complete and when our report might be finished,” Fuller wrote, “nor was any information provided to us from those offices.”
The firm released a scathing report into Rosenberg in May, concluding that the Amherst Democrat suffered from “significant failures of judgment and leadership.” It determined that Hefner repeatedly interjected himself into Senate business and that Rosenberg gave Hefner unfettered access to his official e-mail.
Rosenberg resigned from his Senate seat within days.
Efforts to reach an attorney for Rosenberg were not successful Monday.
Healey’s office later brought charges against Hefner, who pleaded not guilty in April to five counts of sexual assault, four counts of distributing nude images without consent, and one count of criminal lewdness.
Prosecutors said Hefner groped two men against their will, kissed another “aggressively on the lips without his consent,” and boastfully showed nude photos of a fourth man who said he had never agreed to have the pictures taken.
The Senate on Monday submitted a 37-page filing in Suffolk Superior Court formally opposing Healey’s office’s request for a court order for records on “additional” accusers who spoke to Hogan Lovells attorneys.
Jennifer G. Miller, the Senate counsel, called on the court to deny the motion, and accused Healey’s office of “fishing.” Miller said Hogan Lovells attorneys did not create formal, written statements for any of the 45 witnesses they interviewed, but in two instances, witnesses did provide informal written statements.
One witness, who was a State House employee at the time and identified as Witness A in court filings, provided Senate investigators with copies of texts with Hefner as well as e-mails in which the witness “referred” to Hefner sending a photograph of what he said was Hefner’s penis.
Neither the texts nor the e-mails were part of the records the Senate had previously produced for state and federal authorities.
The other person, Witness B, told investigators that Hefner had “engaged in unwanted touching of a sexual nature,” including grabbing the witness’ genitals.
Miller wrote that it appears Healey’s office “is interested in the e-mails and screenshots to discover the identities of Witness A and Witness B.”
“Presumably, the Commonwealth would like them to testify about other alleged bad acts by defendant Hefner,” she wrote, arguing that prosecutors are seeking their identities “particularly to learn more about uncharged conduct.”
She also said if the attorney general is seeking information on additional accusers, it should be able to do so using its own resources.
“The Commonwealth ... fails to explain why it could not uncover the same persons and information – about different, uncharged conduct – through its own, parallel investigation,” Miller wrote. “In fact, the Commonwealth was better-equipped to discover the information it now seeks because it had grand jury subpoena power.”
If the Senate is ordered to turn over any documents, Miller said, it should be limited to statements made by witnesses the attorney general has already interviewed and intends to call to testify at trial.
Senators have said they’re committed to keeping witnesses in its investigation confidential, though Senator Michael J. Rodrigues, who chairs the chamber’s Committee on Ethics — which hired Hogan Lovells — told the Globe last month that the chamber would not violate a court order.
“We promised anybody who came forth at the time that we would give them confidentiality. That’s very important,” Senate President Harriette L. Chandler told reporters at the State House. “That was our word to them. . . . To deny that now would be to turn our backs on a promise that was made.”
Hefner is also opposing the attorney general’s request, arguing that the focus of the Senate investigation has “no relevance” to his criminal case.
A hearing in Hefner’s state criminal case is scheduled for Tuesday in Suffolk Superior Court.