But isn't it logical that the severity of the outcome is what punishment should be based upon, rather than the tool involved?
Not entirely - in most cases the matter of intent is equally or perhaps more important that the outcome.
If I deliberately pulled my gun out and put it to your head and pulled the trigger and you died that is one thing - but if we are out hunting together and I trip and fall and my gun fires and you are hit and die - the outcome is the same - but the intent is quite different. Forgetting negligence and proper firearm handling - the key difference is intent.
I think that may be why so many people get off or light sentences with drunk driving "accidents" because they did not intended to ram their car into another vehicle or a pedestrian. Of course getting behind the wheel while intoxicated should be treated as intent to cause harm.
Consider a case in the parking lot where my sister works. A shopper had finished emptying her cart as a man walked by and asked if she was done with that cart and could he take it - she was - he did and took about two steps before another car smashed into the woman placing her last groceries into her trunk. While I do not know the outcome, the woman shopper was seriously wounded and based on the description I heard I wouldn't be surprised if she lost at least one leg. On review of the store video they found that the woman whose car had stuck the shopper had gotten into her car, started it and put it in gear as she was closing her door when a gust of wind pulled the door open and dragged her out of the car leaving the running car, in gear, to accelerate across an open parking space and the lane into the woman shopper who was injured.
Clearly the second woman did not intend to ram her car into another person causing serious and likely permanent, life altering injuries. Was she even negligent in putting the car in gear with the door open? (Did she have her seat belt on? I think not likely since she was pulled free of the car).
If the second woman had still be in the car but put it into drive instead or reverse, would she be more or less culpable in the resulting injuries?
If the second woman had been under the influence, what then?
If the second woman had been on the phone, what then?
With any nuance of circumstance that led up to the injury it is all too easy to react emotionally and say that the punishment should be severe since the outcome was severe.
When we say that the punishment should fit the crime - lets be careful to make sure we understand exactly what the crime is based on all the facts in the case and not just the result, unless of course you are with the Ferguson protestors.