I would not tell someone who supports the death penalty that it was unBiblical. The problem isn't the Bible, it is all the corrupt prosecutors and judges who are willing to try and convict those whom they may actually believe may be innocent, even if they have to ignore the rule of law in doing so. to to many prosecutors, it is not about justice; it's about winning; and that is wrong.
Good.
You have your reasons. You have the experiences to have those kinds of reasons.
All I require is absolute certainty that the murderer is the one being executed. If that cannot be absolutely guaranteed, then I don't support the execution. When it can absolutely be guaranteed, then I have no problem with the execution.