From Scientific American:
Last December was a special month for U.S. executions. North Carolina gave a lethal injection to Kenneth Boyd, making him the 1,000th person to be executed since the 1976 Supreme Court decision to allow the reinstatement of the death penalty. Soon thereafter, on December 13, California put to death Crip gang founder Stanley “Tookie” Williams. The U.S. remains the only developed Western nation to permit executions despite serious flaws in the system. No need for any pacificist proclivity or liberal leaning to see that–just look at the science.
First, there’s DNA evidence. Although it cannot prove guilt beyond all doubt–who can forget O.J. Simpson?–it can definitively prove innocence. The first DNA exoneration occurred in 1989, and since then many on death row have been set free because of it–the Death Penalty Information Center counts 122 exonerations since 1973. It showed that too many convictions resulted from sloppy or overzealous police work and prosecution, or incompetent defense attorneys. It helped convince then Republican governor George Ryan of Illinois in 2003 to declare the death penalty “arbitrary and capricious” and to commute the sentences of all 157 inmates on the state’s death row.
But DNA isn’t the only contribution from science to this issue.
More here.