Muhammad A. Aziz and Khalil Islam were convicted of killing Malcolm X 55 years ago, and now the two men will be exonerated over evidence withheld by the FBI and the NYPD, the New York Times reports.

Aziz and Islam, who were previously known as Nation of Islam members Norman 3X Butler and Thomas 15X Johnson, are expected to have their convictions tossed according to the men’s lawyers and the Manhattan district attorney. The news comes after a 22-month investigation from the lawyers and the Manhattan district attorney’s office, which deduced that prosecutors, the New York Police Department, and the Federal Bureau of Investigation withheld evidence that could have led to Aziz and Islam’s acquittal.

The two men were arrested following Malcolm X’s assassination on Feb. 21, 1965, and maintained their innocence ever since. Three gunmen opened fire on the civil rights activist at Manhattan’s Audubon Ballroom, and Nation of Islam member Talmadge Hayer—now known as Mujahid Halim following his conversion to Sunni Islam—admitted to his invovlement in the killing. He did not identity the other two, but asserted that Aziz and Islam were innocent and not the gunmen on multiple occasions.

Manhattan district attorney Cyrus R. Vance Jr. said that law enforcement failed the two men's families by quickly arresting them on questionable evidence. The investigation has proved difficult, however, as many witnesses, investigators, and potential suspects have since died. Important documents, including murder weapons, are also no longer available. "This points to the truth that law enforcement over history has often failed to live up to its responsibilities,” said Vance. “These men did not get the justice that they deserved.” 

FBI documents have detailed how there were two undercover officers in the ballroom at the time of the assassination, but this information was not disclosed. NYPD files, meanwhile, show that a reporter received a tip the same day that Malcolm X was going to be killed. “This wasn’t a mere oversight,” said lawyer Deborah Francois. “This was a product of extreme and gross official misconduct.”

Islam was paroled in 1987 and died in 2009, while Aziz was paroled in 1985.