>Jim, every year, prison guards and other prison employees are either killed or injured by those doing time for first-degree murder.

So that possibly is an instance where the death penalty could continue to apply. I'm assuming that there would be direct video evidence of the perpetrators doing the deed.
Although, since it happens even with the death penalty in place, I don't see how that would make any difference. Other than to salve the "need" of death penalty proponents.