A penalty in the NFL that can cause a lot of drama is roughing the passer. This rule means that no player on defense is allowed to make contact with the quarterback after the ball has been released from his hands. Unless the defender is carried by his momentum and can’t stop, he is not allowed to come in contact with the quarterback at all. The only time a defender is allowed to touch or hit the quarterback is if the ball is still in his hands and he has not thrown it or handed it off yet.
When the quarterback is still holding the ball and he gets hit, it is usually called a sack. A sack means that the defender tackled the quarterback when he was waiting to throw the ball, and the offense loses as many yards as the quarterback dropped back. Roughing the passer, however, is a penalty against the defense. It will result in a 15 yard penalty against the defense and an automatic first down for the offense.
The referees have to always be the judge as to weather a hit should be called as roughing the passer. If a defender is carried by momentum and it is obvious that a hit to the quarterback after the ball was released was not on purpose, the flag will most likely not be thrown. However if it is obvious that a defender hit the quarterback after he threw the ball intentionally, the flag will always be thrown and the penalty will be called. Sometimes the refs throw the flag when they really shouldn’t have, and this gets the fans in the stadium riled up, especially if the defense who got called for the penalty is the home team.