The case again had raised tensions about racism in the U.S. South, as Nifong framed the situation as a racially motivated attack by privileged white students.
Monday's letter is a formality. Nifong already had been disbarred, suspended from office and replaced by his old boss as Durham County district attorney for his handling of the discredited rape case. He also had submitted a resignation letter last month that was to take effect July 13.
But a Superior Court judge moved ahead last week with an effort to remove Nifong from office under a rarely used process established in North Carolina state law. He held off kicking Nifong from office until Monday, allowing Nifong time to send Governor Mike Easley a new letter of resignation.
Last month, a disciplinary committee of the North Carolina State Bar found that Nifong broke more than two dozen rules of professional conduct while investigating a woman's allegations she was raped at a March 2006 lacrosse team party where she was hired to perform as a stripper.
Nifong won indictments against three Duke athletes even though he knew DNA testing had identified genetic material from several men — none of them members of the lacrosse team — in the accuser's underwear and body. He did not disclose that information to defense attorneys for more than six months.
The disciplinary committee concluded his actions were designed to help him win his first election as district attorney, in 2006.
The three players, who had called the allegations against them "fantastic lies," were cleared in April by North Carolina Attorney General Roy Cooper. He said they were the innocent victims of Nifong's "tragic rush to accuse."
In tear-filled testimony at his ethics trial last month, Nifong promised to resign, saying "My community has suffered enough."