[Double Naught Spy]

If you walk into your home and find an intruder and draw and fire a weapon who is really the agressor from a legal point of view?

I don't think the issue is so much one about who is the aggressor as it is about who is the threat to me in my home. The intruder is the threat, whether he walks in on me in my home or I walk in on him in my home, he is a threat. I sincerely hope that I am the first to take action because the threat needs to be mitigated, whether that means downed or in flight from my home. I certainly don't want to be the second person taking action if I run into an intruder in my home.

And are warning shots ever a good idea?

I am not a fan of warning shots, but at the same time I cannot argue with all the instances in which they have worked (regardless of the legal consequences which I am not involving here).

I asked a cop about that once.
He said the warning shot is a warning another one is on it's way.

Sounds like a decent enough answer to me

So a warning shot is a warning that another warning shot is on its way?

From my own personal perspective, a warning shot is not an indication of a willingness to shoot another person, but more of an indication of an unwillingness to shoot another person. The person firing the warning shot is not doing it for the benefit of the person being warned (though often portrayed as such) as much as doing it as a non lethal show of lethal force because the shooter mentally isn't prepared to shoot another person.

If you think you need to warn a person that another shot is on its way, then I think it is clear that you are hesitant to fire at another person. In other words, you are taking indecisive action, demonstrating a force you don't want to use.

Back when my pop became a cop in the 1950s, they taught things like warning shots, but they have fallen from favor for numerous reasons such as those mentioned in this thread.

Warning shots are a scare tactic and some people will be scared by them. The big problem I see that is if they aren't scared, then you are now down 1 round from which to begin to deal with your threat.

If you are justified in using lethal force against another human because that person is showing intent, opportunity, and ability to do serious bodily harm or cause death to you or a loved one, then why would you waste a shot? If there is intent, opportunity, and ability to do such harm, do you really want to waste time and ammo hoping that the bad guy might be scared by the warning shot? You are at a point where the time for warning may already be passed and it is now a time for action.

Of course, it is all very situational as Uncle Buck's circumstance indicates. Warning shots can work, but certainly don't always work.

True story about a warning shot...
When my grandmother died, I helped my mom cleaning out my grandmother's house. It was where my mom grew up. Mom found a piece of slate (an old chalkboard) that hung in a closet of the house and it had a hole in it. My grandfather traveled for business and was away from home a lot. Early one morning came a pounding at the front door. Grandmother called out to ask who it was and the pounding just persisted and got louder. Fearing a person was wanting to break in, she gathered my mother and uncle together so they would be safe and she fired a warning shot into the closet at the chalkboard...which it went right through (go figure)...and the pounding soon stopped. Success! A potential intruder scared off. No.

Turns out that the guy knocking on the door was a deaf man that lived down the street several blocks. His family and my family were good friends. He had walked the several blocks to catch the train to go into town to work but had taken with him the money needed to pay the rent that day. Fearing he would be late to work (which you didn't want to be during the Great Depression), he had stopped at grandmother's house hoping she would take the money back to his wife so that the rent could be paid.

In the end, the knocker never heard the shot. He was deaf, LOL. He ended up running home with the money and caught a later train, was late for work, but did not get fired. Warning shots don't work if the person being warned doesn't know you are firing a warning shot.