A SIMPLE PROBLEM TO PASS A SATURDAY MORNING

The four boys below cannot turn their heads, ie they can only look in the direction they are currently facing. There is a brick wall between Jim and Gene. The four boys are told that they are wearing 2 black and 2 white hats.

They are then asked if anyone knows what color hat they are wearing. After a minute's time, one boy says with 100% certainty which color hat he has on.

Question: Which boy knew and how did he know with 100% certainty.

BTW, I just noticed that the two lawyers have black hats -- a Freudian slip.