And in a way it makes sense if the dad saw that it was likely that it'd eventually come out who threw it, then he could now point to turning him in to say "look, we're cooperating, and this is a good kid with no prior so we think leniency is appropriate".  Now add to the mix good lawyer also who could drag the case out and make a conviction very burdensome, if not unlikely, and a DA will often decide to focus their resources elsewhere, and something like this will just get a gentle wrist slap.  

I of course have no idea if this actually is happening.