Maurice Caldwell spoke in favor of the Safe California Act, a ballot proposal that would end capital punishment in the state and replace it with life in prison without the possibility of parole.
Caldwell says he's proof the criminal justice system makes mistakes.
Proponents began gathering signatures Tuesday and plan to put the initiative on the November 2012 ballot.
Death penalty advocates say the issue will just vitalize conservative voters during a presidential election.
A recent Field Poll found a vast majority of California voters support capital punishment, but if given a choice, more prefer life in prison over the death penalty.