How ironic! Shot his beautiful woman on valentines days and gets sentenced on 9/11.... What's with guys shooting chicks and throwing chicks of stuff! The world is getting f#cked up!

Legally, he doesn't have a leg to stand on

I think it's a few crossed wires in the brain. The connections start to form before birth and continue on for years, but the initial pattern is established before birth.
Genetics can give a predisposition towards the way connections form, but are not a determining factor.
The same genetics can result in many different personalities but have a tendency towards similarities.
There have been a number of interesting and informative studies on this using identical twins, non identical twins, and siblings.
The connections are also influenced by external events as to how they form up but the external influences will still be working with the base personality type provided by the genetics.
Most misconnections are of little or minor consequence and can be overridden by training and an adherence to social convention, however, sometimes some people are unfortunate enough to get a pattern which they simply cannot control.
Under the right trigger circumstances they just explode.
Things which might just annoy the hell out of someone else, sends them into an explosive rage., and hang the consequences.

They can be all very remorseful after the event but often feel it was the other persons fault for doing something which they think they should have known would set them off. I think Pistofficus would have that attitude and hewould still think it was his girlfriends fault for provoking him.
On that basis they feel their actions were in some way justified.
They usually don't think much of the blame lies with themselves.

I have no doubt that the shock Pistofficus shows is genuine, but it's the shock of seeing the results of his own actions rather than the shock of seeing that it was not an that intruder he killed.
I don't believe he ever thought he was shooting at an intruder when he fired the gun.
He absolutely knew he was firing at his girlfriend and he was 'going to teach her a lesson'.
His problem was, that in his rage, he did not think through the event any further than that.
What's the good of a lesson if the recipient is dead?

I agree Pweedas everyone is programmed to some extent and I myself must always be on guard!
Its not that I'm a 'bad' Person it's just a rage inside, a self protection mechanism from nature Maybe.
I think there should be Even a bigger difference between spur of the moment and planned murder, with
sentencing.
As for guilt of this man, we all know how the media give small bits of info to lead us along!
Unless you are in court and hear the whole case then it would be to easy to jump to conclusions.