Two of the men found guilty of the assassination of Malcolm X are expected to have their convictions thrown out on Thursday, the Manhattan district attorney and lawyers for the two men said, rewriting the official history of one of the most notorious murders of the civil rights era.

The exoneration of the two men, Muhammad A. Aziz and Khalil Islam, represents a remarkable acknowledgment of grave errors made in a case of towering importance: the 1965 murder of one of America’s most influential Black leaders in the fight against racism.

A 22-month investigation conducted jointly by the Manhattan district attorney’s office and lawyers for the two men found that prosecutors and two of the nation’s premier law enforcement agencies — the Federal Bureau of Investigation and the New York Police Department — had withheld key evidence that, had it been turned over, would likely have led to the men’s acquittal.

The two men, known at the time of the killing as Norman 3X Butler and Thomas 15X Johnson, spent decades in prison for the murder, which took place on Feb. 21, 1965, when three men opened fire inside the crowded Audubon Ballroom in Manhattan as Malcolm X was starting to speak.

But the case against them was questionable from the outset, and in the decades since, historians and hobbyists have raised doubts about the official story.

The review, which was undertaken as an explosive documentary about the assassination and a new biography renewed interest in the case, did not identify who prosecutors now believe really killed Malcolm X, and those who were previously implicated but never arrested are dead.

Nor did it uncover a police or government conspiracy to murder him. It also left unanswered questions about how and why the police and the federal government failed to prevent the assassination.