Here's another, "Parent Friendly" Hint:

Have you ever met up with the problem of trying to get the truth out of children that won't "rat" on each other?  An admirable trait, but sometimes you just need to find out what the heck is going on!

Ask them to line up in a straight row and stick out their tongues.  Tell them that you can actually figure out who is telling the truth by their tongues.  Now, of course it is their eyes and body language that will be the strong clues you are looking for ..... but you know that and they don't!  (O:

This tip I cannot take credit for.  I read it somewhere and thought it was great!