A good judgement call happens if the ball is being shot on goal, hits a player's hand, and changes direction. Was it unintentional? If yes, still award the PK b/c it took away a goal scoring opportunity.
If the ball is in the box, hits a hand or arm, and it was unintentional, then it should not be a pk. But shots on goal that hit hands or arms, whether intentional or unintentional, should be pks.
