Ever since his release from the Adirondack Correctional Facility in Ray Brook, N.Y., Mr. McKee, now 47, has been learning to live in a very different world than the one he left in 1997. It is a difficult adjustment that parallels the experiences of many others who have been released in recent years after serving time for wrongful convictions.

“Technology’s changed,” he said, holding his iPhone 8 curiously. “The phone. I’ve still got problems with it, with emails and texts.”

A jury found Mr. McKee guilty of murder after a 16-year-old witness testified that he saw Mr. McKee shoot Theodore Vance, 29, after a fight on the corner, at 176th Street and University Avenue. The fight turned into an all-out brawl in which brickbats and other debris became weapons.

Prosecutors and defense lawyers agree Mr. Vance struck Mr. McKee with a pipelike object during the melee, and then was shot by someone. Mr. McKee insists he ran away before the shot was fired. The gun was never recovered.

Mr. McKee was released after a new witness came forward last year and gave a different description of the killer. The Bronx district attorney’s office, after a six-month investigation, also determined important grand jury testimony was never shared with the defense. A person who knew the victim told the grand jury that in his last moments, the man had described his killer as a “Spanish guy.” Mr. McKee is black.