There are two issues involved with the death penalty. One is the fact that it is fairly easy to get some people to confess to anything, including murder, despite their innocence. And there is also the fact that eyewitnesses are often very inaccurate. There is a skit used by some law schools where a fake murder is carried out during an assembly of future lawyers. One guy goes running down the aisle screaming, and another chases him and shoots him with a gun. Then the students are asked for as thorough a description of the action as gthey can write. Only a small percentage can pick the 'murderer' out of a line up, and many confuse the victim with the shooter.
The other issue is competence of the executioners, if the death penalty is used. The other is the incompetence of the jailers, who lose a few prisoners, even murderers, to escape.
Of course, we all wanted the guy in the Shawshank Redemption to get out, didn't we? If Maine were a capital punishment state, he wouldn't have had a chance to bust out of Shawshank.
So if we must have a death penalty, it needs to be accurate and swift, or not at all.
If we put murderers away for life, then we need better prisons and guards.
I think a guillotine would be preferable to a scimitar, but since even France has abandoned it as inhumane, it would be accused of being far too unusual. I think public beheadings are rather barbaric regardless of tactical