http://en.wikipedia.org/wiki/Henry_Lee_LucasBasically, a serial killer who confessed to thousands of murders, recanted all of them, then confessed to others. Fascinating story of the gullibility of cops and the twisted mind of a deranged man. No one really knows how many people he killed. Certainly his mother. Almost certainly his under-age lover and an elderly woman who tried to help him. Probably a dozen or more. Maybe even hundreds, though it's doubtful.
He was partners with Ottis Toole, the man suspected of killing Adam Walsh. Toole himself was convicted of six murders in Florida, though he never stood trial for Adam Walsh.
I had a friend who worked homicide in Texas, who had heard one of Toole's confessions about someone he and Lucas raped and killed. Some of the things he said, you wouldn't believe a person would do.
His death sentences was commuted to life because the one murder he was sentenced to death for was clearly committed by someone else. Lucas wasn't even in the state. But prosecutors and investigators were so eager to believe whatever Lucas confessed to that they didn't do the basics, and because of it, Lucas was convicted and the real killer remained free. Later, they decided that since they weren't really sure Lucas had killed anyone (he had already served time for killing his mother), they would commute his death sentence to life. That way, they could keep him in jail for a crime they knew he didn't commit since he probably committed some other murders, though they just weren't sure which ones. Lucas didn't care, he got better treatment in jail than 50% of Americans get out of jail, and no one seemed to fuss about it.