Well, then the parents were given wrong advice. A little emotion (tears) would have gone a long way with me, if I had been on that jury.
You should try crying when you're being tried for cold-blooded murder. Maybe you'll be lucky and get someone like yourself on the jury.
Better yet- cry in every situation possible... speeding tickets, paper-cuts, bad haircut. If a little emotion is good, then a lot must be even better!