Very practical idea, but moral clarity it ain’t.
Here is moral clarity: If you kill someone or attempt to kill someone you forfeit your rights including the right to life. Why should someone get a lesser sentence for attempted murder? Their intention was to murder but they just weren’t successful at it. The reason there is so much evil in the world is because society allows it.
Why not?
You DO realize that "I don't agree" is neither a moral or legal argument and, indeed, is no argument at all?