Is trespass a justified reason to kill someone?
Trespass and probable cause.
Meaning you are beyond a reasonable doubt that this person carries ill intent.
Probably. If they are in your house uninvited when you're in it, it's reasonable to assume they are a serious enough threat to swat them hard with the bat a few times first and find out what they were really up to if they wake up later.
Don't steal from me and you're good.. just stay off my lawn
Legally, if they are outside your home, no. If they enter, probably.
That depends on what is involved in the trespass. Home invasion with intent will be met - in my case - with deadly force. And I will be the sole decider on whether or not there is intent. I will acquire the target and fire - twice. That will be enuff