Eighteen years ago, Waters was found guilty of beating and stabbing to death Katharina Brow during a 1980 robbery. As CBS News Correspondent Jim Axelrod reports, his defense was as is common in prisons, shackles and bars.
"I told them, 'I didn't kill nobody, man. I don't know what you people are talking about,' " Waters said.
His lawyer at the time argued Waters was in court on the morning of the slaying to face a charge of assaulting a police officer.
The trouble was, nobody in Massachusetts believed Kenny Waters. Well, practically nobody. There was his sister. She was a high school dropout, with two kids, no job and a crazy idea.
"One day I just said, 'I think I'm going to law school' and he was very excited… and he just said 'yes!' " Betty Ann Waters said.
Ms. Waters had a big plan, but also a lot of doubts. Her brother didn't because he'd been leaning on his kid sister for years.
"I knew how smart she was… every time I copied her papers I got As," Kenny Waters said.
Twelve years after Betty Ann Waters went back to college, she graduated from law school.
"I'm the type that has to do something... so I just kept doing something until I got to the end," Ms. Waters said.
Inside this prison, Kenny had tried to kill himself. Outside, his sister kept digging. After graduating, she focused on her brother's case, and to this day has taken only a few other cases on behalf of friends.
The breakthrough came when she hounded the clerk at the courthouse and learned that a box of evidence with her brother's name on it was in the basement. The box contained the knife used in the slaying and pieces of cloth with blood on them.
She enlisted the help of the Innocence Project, a group that helps inmates challenge convictions with DNA evidence. The material was tested, and the district attorney's office announced Tuesday that the DNA she found did not match her brother's.
"She did re-investigation. She got recantation from the witnesses. She came to us with a strong case," said defense attorney Barry Scheck, who heads the Innocence Project.
Her brother was obviously thrilled.
"I'm just really happy my brother is sitting right here next to me right now.. It's still not real yet," she said.
Kenny Waters is the 85th prisoner in America released in the face of contradictory DNA evidence, but he's not thanking science. He's thanking a sibling.
"Sisters are the best things in the world. Always take care of your sisters. They'll take care of you," he said.
In the end, Kenny Waters was freed by his blood — the kind that held critical clues, and the kind that kept searching for them.