SPB> the death penalty is hardly an effective deterrent, is it?

I believe it used to be at least partially effective in the UK; witness the slow rise in murders, manslaughter, gun crime etc since its abolition. Statistics to help disambiguate this point will be warmly welcomed. (Outraged headlines don't count, as by definition they don't reflect business as usual, otherwise they wouldn't sell newspapers. But that's a rant for another day.)