Best to read up tbh. In a nutshell an off-duty cop playing good Samaritan was shot and killed in 1989. Nine witnesses said the guy now on death row was the killer, even though no gun was found. To date, seven of the nine witnesses have come forward to recant their statements saying they were made under duress from the police (eg 'Finger the guy or we'll prosecute YOU for the murder instead').
There's a question mark over whether the ballistics evidence was fabricated also, and the guy maintains his innocence. In fact one of the guys who originally pointed the finger (Cole) seems to be a potential suspect out to save his own skin. He admitted owning a .38 handgun (as used in the killing) but said he'd 'given it away' earlier that night...
Unfortunately he seems to have been an ordinary guy in the wrong place at the wrong time. At any rate not what you'd call a 'safe' execution by any means.