Again, you are talking about outside the home. The standards are much lower inside your home.The key words are "reasonably believe". In the middle of the night, I hear an unfamiliar voice call from downstairs "hello?" Not sure if its the next door neighbors drunk kid or someone there to rob me. Is it reasonable to believe that a stranger in my house at 2am is there to rob me? A discussion online asked this question and said the requirement is for someone to prove you were wrong in your belief, not for you to prove you were right. Part of the litmus test is, does another person, given what you observed and the situation details feel the same as you? Personally, I would evaluate the situation to some degree and really would not want to spend the time and money in court resulting from a shooting BUT, rather that than dead. I dont think it is unreasonable to think a stranger in my house late at night is there to rob me (or worse). Heck, people dont visit during daylight hours, what good deed would posses them to visit me at night?
If it even goes to court, its pretty easy to justify.
It can be impossible to distinguish a good guy from a bad guy in low light and with adrenalin pumping.
You can use any means necessary to remove the threat from your house.
You have no obligation to retreat or interrogate the intruder.
90% of the time you may be able to tell if they are a threat or not. But that other 10% could cost you your life.