"Yes. But what about the man who unsuccessfully punches someone with intent to kill and the man who punches someone without intent but kills them anyway?"
The formers 'failure' gets him off the hook
The latter is (is he ?) less of a danger to a population which he has reduced by 1 and is malleable enough to have learnt a tragic lesson
What if the former has a history of failures (the 2nd time) ?
One 'free strike' and you are out (or 'In') ?