Too Old To Execute?

Whatever your opinion about capital punishment, the argument that just because a killer of four people is now too old and sick to execute after burning up 20 years of appeals just doesn't fly with me. After all, thanks to him, the four people that Clarence Allen murdered never got a chance to get old and sick themselves. The cruel side of me wants to retort that if he's that sick, then maybe we could think of his execution as euthanasia.