More confirmation of a long-held bias of mine: Whenever I see an unfamiliar guy strolling around the neighborhood at odd hours (or any hour, for that matter) wearing a flipping BACKPACK, it is always a red flag to me. I can't help it. If I see them on my cameras, I always keep watching. If you look at YouTube videos of residential thieves and burglars on surveillance cameras, it's like a backpack is part of their standard uniform. Yes, there are a few innocent reasons why somebody might need to be strolling around on foot among houses and yards with a big backpack strapped on. Maybe he's a neighbor kid who's well-known for carrying his books home from school, etc. But if it's a stranger, he's a suspicious person every time, far as I'm concerned. The backpack is the giveaway. Just my personal (paranoid) opinion.