BROOKLYN (WABC) -- It was an emotional day for a man in Brooklyn who had his murder conviction overturned for a crime he did not commit.
Derrick Hamilton spent 21 years in prison until it was revealed that the detective in the case threatened a woman to testify against him.
On Friday, Hamilton's conviction was thrown out.
Clutching his daughter and his new life, the 49-year-old Hamilton was formally exonerated in the 1991 incident.
"One day in prison is too much for an innocent man," he said outside court. "It's exhilarating. It's a grateful day."
The only eyewitness in the case recanted her testimony years ago, saying she had been strong-armed by disgraced former NYPD detective Louis Scarcella, a discredited cop whose tactics have led to the review of multiple cases and the release of several wrongly-jailed defendants.
The dismissal marked the fourth time a conviction involving Scarcella has been vacated amid one of the nation's most ambitious efforts to determine whether old cases were mishandled. About 100 convictions, including roughly 70 linked to the retired detective, have come under scrutiny by Brooklyn District Attorney Kenneth Thompson.
The investigation by the DA's Office led to the full vindication.
The review found that the girlfriend had testified that the victim was shot in the chest by a lone gunman despite medical evidence he was hit in the back. It also uncovered ballistic evidence that there was more than one gun fired.
Hamilton had maintained his innocence from the start, and over the years, the inmate steadfastly refused to admit guilt, even when it hurt his chances for an earlier release by the parole board.
"I couldn't say I killed a man I didn't kill," he said.
He was eventually paroled in 2011 before taking a job as a paralegal.
Hamilton admits he is bitter, but he used the time behind bars to study up on the law and is now helping others who have perhaps been wrongfully convicted to find justice too.
Asked if he harbors any resentment toward the witness, he said, "I think she was a pawn. She was as much a victim as I am."
Thompson released the following statement after the conviction was thrown out:
"Wrongful convictions ultimately destroy the lives of the people who are wrongfully convicted, as well as their families, and also do great damage to the integrity of the justice system. The people of Brooklyn elected me to ensure that justice is done and that is what my decision to vacate Derrick Hamilton's conviction reflects. The Conviction Review Unit carefully analyzed the scene of the crime and based on the scientific and medical evidence concluded that the sole eyewitness' account was unreliable."