The American Kirk Bloodsworth spent almost nine years in prison - two of them in the alley of death - before he confirmed what he had always known but could not prove: that he was not responsible for raping and killing a 9-year-old girl near Baltimore, in 1984.
What ultimately helped Bloodsworth and allowed him to get out of jail was a practice that in recent years has become common, but at the time it was a rarity: the comparison of samples of genetic material.
In 1993, Bloodsworth became the first person in the United States to be sentenced to the death alley and then released based on his DNA, although by then his sentence had been replaced by two consecutive life sentences.
His case became emblematic, he has been the character in books and interviews and there is even a program in his honor, part of a 2004 law, to help defray the costs of DNA testing after a conviction.
Bloodsworth spoke with BBC Mundo about his effort to eliminate the death penalty, his most painful moments in prison and how not a day goes by without him thinking about everything he had to endure.
Bloodsworth, who was recently married when he was arrested at age 23, says it was a book that saved his life.
As a prison librarian, I spent a lot of time trying to read everything that fell into their hands: newspapers, treaties, court cases. Anything that could help him prove his innocence after he was convicted of the crime of little Dawn Hamilton based on eyewitness testimony.
At that time in prison he met a book by writer Joseph Wambaugh that details how DNA had been used to arrest the guilty party of a crime in the United Kingdom.
Bloodsworth, then, had what he calls his "eureka moment": "If one can condemn someone for DNA, one can also free someone through DNA", he says he thought.