The side effect that won the man his court case is called gynecomastia, which is an enlargement of male breast tissue. The plaintiff in the case began taking Risperdal at age 8 for irritability associated with autism and developed size 46 DD breasts in his early teens.
What was at issue here was not that the side effect was possible, but that the prescribing doctor was not made aware of the possible risk even though one study showed gynecomastia as a potential side effect. This was the first case involving the condition that went to a jury trial, but there are others lined up in several states.
You can read more about this case here at philly.com.