Humans aren't perfect and mistakes will happen, killing all the inmates on death row will not justify the few innocent deaths that will inevitably occur under that type of policy.
this should be contingent on the circumstances and not be a black or white rule. In the case of the nuremberg trials, a series of capital punishments were used. As such, extreme cases should be grounds for revising of such a law, where there is no doubt of guilt and no chance for rehabilitation