The other day I went to a talk by Nick Yarris.
He was sent to prison in 1981 and to death row in 1982 for a murder he didn't commit.
After two decades of protesting his innocence and campaigning to be the first death-row prisoner to have DNA testing to prove his innocence, he gave up hope in 2002 and wrote to his appeals judge asking to be put to death.
In January 2004, after the testing proved his innocence, he walked free after 23 years in prison (almost all on death row) - more than half his life (he's now 45).
http://www.nickyarris.com/story.php