The high court ruled 7-2 Wednesday that Kentucky's use of lethal injection to execute prisoners is constitutional but in his concurring opinion Stevens questions whether capital punishment serves any purpose, The Chicago Tribune reported Thursday.
Stevens wrote that when the court agreed to hear the Kentucky case he "assumed that our decision would bring the debate about lethal injection as a method of execution to a close. It now seems clear it will not."
The nation's longest-serving justice went on to say that the death penalty no longer meets any of the societal aims laid out when it was re-instituted in 1976 following a four-year moratorium. Stevens was one of the justices restoring the death penalty.
But this week, he showed a clear change of mind.
"State-sanctioned killing," he said, is becoming "more and more anachronistic."
The Chicago native wrote that modern, lengthy prison sentences have achieved the goal of preventing further crimes.
Stevens said researchers have yet to prove to his satisfaction that the death penalty deters others.