A Pennsylvania man who spent 21 years in prison for murder he didn't commit walked free on Wednesday more than a decade after the star witness in the case initially confessed to the crime. 

John Miller was found guilty of second-degree murder in 1997 for the killing of parking lot attendant Anthony Mullen. Despite there not being any physical evidence tying him to the crime, Miller was accused of fatally shooting Mullen outside of Philadelphia's main railroad station the year before. David Williams, the alleged eye-witness who implicated Miller, told police Miller had confessed to him that he committed the crime, according to court documents. In exchange for his testimony, Williams received leniency for robbery charges in another case, Inquirer reports. 

Williams recanted his statement several times, including at Miller’s preliminary hearing. He confessed to the murder in a letter he sent Miller's mother a letter in 2002. "I can't live with this on my conscience. Your son had no knowledge of this crime," his letter read. "He wasn't even there. I lied on him."

Miller filed a number of appeals over the years, all of which were denied, according to his lawyer Tom Gallagher. He ultimately contacted the Pennsylvania Innocence Project eight years ago, and after his lawyers' appeal to the District Attorney's Office was denied—citing Williams as an unreliable witness—his lawyers appealed to federal court, according to NBC Philadelphia

The federal court ordered for Miller's release, pending the DA's decision to bring forth a new case. Miller's case was then given to the Conviction Integrity Unit, which spent months reviewing the facts, and ultimately found there was "insufficent evidence" tying the wrongfully accused to the crime. “It was quick once they decided to take it,” Gallagher said. “We’re very appreciative there is a robust Conviction Integrity Unit.”

Miller's case is one of nine that have been thrown out since District Attorney Larry Krasner took office last year. According to Assistant DA Patricia Cummings, this marks Krasner's mission to "correct the mistakes of the past."

Hours after he was released on Wednesday, Miller spoke to CBS Philadelphia. “I feel good. I feel amazing, it’s surreal. I’m just very happy,” he told the outlet. “Soon as I stepped out the doors I was just—looked up and was just thankful and blessed for what God has done for me.”