If someone tells me they saw someone jump my back fence, I'm definitely not going outside to check. I'll double check that my doors and windows are secure and call the police. Then I'll hole up in my bedroom and wait. If they enter my house, then I'll take action. I'd hate to go outside and face them, because it'll involve facing lawyers later and there's nothing outside of my house that I'm willing to risk everything for. The lawyers will ask simple questions like "why did you go outside when you knew there was a threat?" and "we're you looking for a gun fight?". Remember, the jury is going to to ask themselves what a reasonable person would do. In this case, a reasonable person would stay inside. Especially in states like mine where you can only shoot to protect yourself, or an innocent person, from death or severe bodily injury.