Public hanging would be good too. You can’t tell me that doesn’t serve as a deterrent! The Left is always telling us how the death penalty is not a deterrent. So what, it’s not called capital deterrence, it’s called capital PUNISHMENT. If it also serves to provide some deterrence then great, we’ll take the serendipity, but we’re not going to quit using it if it doesn’t.
Far as I know capital punishment worked every time it’s been used. I can’t think of a single criminal who has offended after capital punishment is used.