(CNN) An Alabama man convicted of killing three police officers in 2004 is scheduled to be executed Thursday despite questions about his culpability.

Lawyers for Nathaniel Woods, 42, have maintained his innocence, pointing out that another defendant in the case confessed to being the lone gunman.

Woods' attorneys have asked Alabama Gov. Kay Ivey to commute his sentence -- an appeal also made by a number of activists, including Martin Luther King III.

The son of the civil rights icon wrote in a letter to the governor: "In just 2 days, your state, and the state I was born in, is set to kill a man who is very likely innocent."

"Killing this African American man, whose case appears to have been strongly mishandled by the courts, could produce an irreversible injustice," he wrote.

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