In Texas I beleive the law's like:
1) after dark, anyone stealing something significant (like a car) and you have a reasonable expectation not to get it back, you can use deadly force
2) if someone breaks into your domicile and you are "trapped" or fear for your life, you can use deadly force
3) you can carry a concealed handgun (lisenced) and there are a whole host of rules when and how to use it, of course, anytime.

Net result: violent crime is down in Texas (especially after the concealed handgun law)- go figure???