Well, first off, u/Kienan 's ideas are far more workable as things stand right now. Just change the law to increase sentence length and eliminate parole. Legally speaking it's pretty straight forward. As far as costs, I don't know if it's true, but organizations that oppose capital punishment claim its more expensive (legal costs associated with numerous appeals?).

My "hang the bastards" approach would require significant overhaul of the legal system.