Always? Certainly I would never personally grass up someone who was, say, working and claiming dole or who'd nicked something from Woolies - but if I knew they'd mugged and beaten up an old lady then yes, like a shot.it's wrong!
As I said I think it's all down to where you personally draw the line, but if you can cover up for one of your friends or family who'd done something like I've just mentioned ... well I'm glad you're not one of my friends.