The chief judge of the District’s federal court retired Wednesday, citing unspecified health issues that he said prevented him from continuing to serve on the bench.

Chief Judge Richard W. Roberts’s early retirement came on the same day that a Utah woman filed a federal civil rights lawsuit accusing him of sexually assaulting her decades ago when she was a 16-year-old eyewitness in a high-profile murder case that Roberts was prosecuting.

Roberts, 63, declined to comment on his retirement or the lawsuit, but his attorneys called the allegations “categorically false” and said Roberts intends to “vigorously challenge” the allegations in court. His lawyers said the judge, who was unmarried at the time, had an intimate, consensual relationship with the woman that did not take place until after the end of the trial in which she testified.

“Roberts acknowledges that the relationship was indeed a bad lapse in judgment. However, the relationship did not occur until after the trial and had no bearing on the outcome of that trial,” according to the statement from his attorneys, led by Reid Weingarten.

A report from the Utah Attorney General’s office, which investigated the woman’s account, concluded that her allegations were not “strong enough to support a criminal prosecution.” Under Utah laws in 1981, according to the report, the then-teenager was old enough to consent to sexual relations.

Richard W. Roberts (Beverly Rezneck/U.S. District Court for the District of Columbia)

The woman’s lawsuit says that more recent email exchanges with the judge triggered her memories of the alleged abuse.

The 25-page Attorney General’s report from 2015 went on to say that Roberts’s relationship with her raised ethical questions about his work as a federal prosecutor 35 years ago. Investigators for the report did not interview Roberts.

Prosecutors have a constitutional duty to disclose any information that might help the defense. The Attorney General’s report said Roberts “likely” should have told the defense lawyers about his sexual relationship with a testifying witness in the murder case.

In her lawsuit, Terry Mitchell, now 51, says Roberts “intimidated, coerced, and manipulated” her into having sex for weeks and that the young prosecutor picked her up from home or the courthouse to take her to dinner and then to his hotel room before and during the trial.

The Washington Post does not usually identify victims of sexual assault. Mitchell is identified by name in the lawsuit and, through her attorney, agreed to be named in this story.

Mitchell and Roberts met in 1981, when Roberts was working in the Justice Department’s civil rights division and assigned to prosecute Joseph Paul Franklin, who had been indicted for fatally shooting two black men who were jogging with white women through a Salt Lake City park. Mitchell, then 16, was one of the women and was called as a witness to testify for the prosecution about the deaths of her two friends.

Franklin was convicted on civil rights violations because the shootings were racially motivated, and was sentenced to life in prison. He was executed by the state of Missouri in 2013 after being convicted as a serial killer in several murders.

Mitchell and Roberts remained in occasional contact by phone over the years, both sides acknowledge. Each were married and had children.

In the statement, Roberts’s attorneys said he has “always had nothing but respect and admiration for Ms. Mitchell” and that their calls and emails through the years have “always been warm, caring, and friendly, which makes these new, false allegations all the more puzzling and disappointing.”

In 2013, Roberts emailed Mitchell a link to an article about Franklin’s execution. The next year, according to the Attorney General’s report, she reached out to Roberts after he had become chief judge of the U.S. District Court for the District of Columbia.

He called her immediately, the report states. During the conversation, Mitchell brought up their sexual relationship during the time of the Utah trial, according to the attorney general’s report.

Roberts said on the phone recording that he did not remember it that way and said he was “very careful about making sure that . . . your testimony happened and nothing, you know, physical went on until after you had finished your testimony,” according to a summary of the phone conversation in the attorney general’s report. Utah is a “one party consent” state that allows one person to record phone calls without the other party’s knowledge.

Roberts, who is perhaps best known for prosecuting the late Marion Barry when he was D.C. mayor, was appointed to the bench by President Clinton in 1998. He became chief judge in July 2013.

During Roberts’s tenure as chief, the district court won an expanded role in handling foreign requests under mutual legal assistance treaties for evidence and information sharing with U.S. authorities.

This winter, Roberts, presided over a civil rights trial that resulted in a jury verdict and the largest ever settlement paid by the D.C. government, $16.65 million, to Donald Eugene Gates, who had been exonerated through DNA for a rape and murder he did not commit.

“Roberts served with honor and distinction as a federal judge for the past 17 years, and he has been a leader in the community. He has always conducted himself with the utmost integrity, honesty, and decency,” according to a statement from his attorneys, Weingarten, Jason M. Weinstein and Brian M. Heberlig. “He intends to vigorously challenge these false allegations in court.”

A spokesman for the Utah Attorney General’s office said the findings have been referred to the Justice Department and to the Senate and House Judiciary committees because of the possible ethical violations.

House Oversight and Government Reform Committee Chairman Jason Chaffetz (R-Utah) said an initial review of the allegations has “caused alarm and distress” and said he would confer with colleagues on the next steps.

Spencer S. Hsu contributed to this report.