There was a fire next to my house once so my friends dragged me down to see what was going on, and we were standing there watching and the police came and asked us if we knew who did it, obviously we didn't! My friend later said even if she did know she wouldn't have told him because she'd probably be killed!
That's the only time the police have ever asked me anything really, apart from when one came into our primary school and asked us to draw a criminal