Speaking at a luncheon at the National Press Club in Washington, D.C., Holder, noting that he was speaking in a personal capacity and not as a member of the administration, said the "inevitable" possibility of executing an innocent individual is what makes him oppose capital punishment.
"Our system of justice is the best in the world. It is comprised of men and women who do the best they can, get it right more often than not, substantially more right than wrong," Holder said. "There's always the possibility that mistakes will be made ... It's for that reason that I am opposed to the death penalty."
He continued: "I think fundamental questions about the death penalty need to be asked. And among them, the Supreme Court's determination as to whether or not lethal injection is consistent with our Constitution is one that ought to occur. From my perspective, I think a moratorium until the Supreme Court made that determination would be appropriate."
Holder clarified that his personal views on the matter are not part of an ongoing Justice Department review of state execution practices.
Last month, the Supreme Court agreed to review a case brought by death row inmates accusing the state of Oklahoma of violating the constitutional ban on cruel and unusual punishment. The case came after Oklahoma botched the execution of inmate Clayton Lockett, who was seen writhing and clenching his teeth after being administered a lethal three-drug combination. Lockett ultimately died 43 minutes after he was administered the drugs.
Holder, who is retiring pending the confirmation of his nominated successor Loretta Lynch, has long been personally opposed to the death penalty.
"I think that the issue is made real when you look at some of the things that have happened in the states over the last year or so, where you had these botched executions, where you had an inability to get the appropriate drug," Holder told The Marshall Project last year. "We've had doctors unwilling to participate in the process. I think this is pushing this country toward some really fundamental questions about -- even though, you know, people still support the death penalty by 55 percent, or whatever the number is -- some fundamental questions about continued use of the death penalty."
H/T The Hill