One of the disadvantages of an editic memory is I remember strange unrelated stuff I have read or heard.
Back in the early '70's NZ had a couple of weekly tabloids who liked to run lurid stories every few months on the death penalty in the US. (they were liberal rags who were not in favour of a death penalty and we had a very popular liberal government at the time, which only lasted one 3 year term, almost unheard of here). I remember the headline of one story reading "Old Sparky Still Going Strong" about a test of the electric chair in one penitentiary. I can still remember the basis of some of the stories written.
About 1972 the SCOTUS ruled the death penalty unconstitutional, claiming the electric chair "cruel and inhumane". For the next four years there were no executions in the U.S.
By 1976 the murder rate across America had risen horribly, especially among police and crime victims. The reasoning went like this:
"If I get caught for this I'm going to jail for a long time. If this victim/police officer lives then the chances of my getting caught increase.
If I kill him I can possibly get away as there is no witness against me. Even if I do get caught I won't be executed, I will just go to jail for a long time, so I will kill him/her and hopefully get away".
In 1976 SCOTUS reversed their decision, While the chair was no longer in favour, lethal injection took its place, with the firing squad being used in Utah for one convicted person in late '76. Over the next few years the murder rates dropped back to per '72 levels.
Just a bit of trivia I bring up when someone says the death penalty does not deter crime.