You forgot one and I was actually going to do a short write up about it because, technically, it's true. It's the number one constant go to after a violent crime where police always state that people are afraid of retaliation if they come forward. Well, that's probably not the sole reason either. I can attest to this as having gone to the police decades ago with information shared with me on my best friends murder, to whom to this day, his body has never been found. Another time on a friend who had been pretty badly beaten many years ago. For me, at least, if you are any kind of friend at all, you'd care enough to try find out what happened to them, but both times they sat there and said "and how do you know this?" As like what level of criminal element(s) are you involved with here. All of a sudden, you feel like you've become a suspect, of something, of whatever you're about to say, somehow connected to it all. And maybe, just maybe, that's why people fear going to the police. They might as well be asking you what part you played in all of this otherwise you wouldn't know all of this. Guilt by association instead of criminality.