Fan interference

In baseball, interference occurs in situations in which a person illegally changes the course of play from what is expected. Interference might be committed by players on the offense, players not currently in the game, catchers, umpires, or spectators. Each type of interference is covered differently by the rules.

The most common incidence of interference occurs when a member of the offensive team physically hinders the defensive team, decreasing its chances to make an out or increasing the chance that a baserunner will advance. Whenever this offensive interference occurs, the ball becomes dead. If the interference was committed by a batter or a baserunner, that player is called out and all other runners must return to the bases they occupied at the time of the interference. If interference is committed by a runner with the obvious intent of preventing a double play, the batter-runner will be called out in addition to the runner who committed the interference. If interference is committed by the batter-runner before he or she reaches first base with the possible intent of preventing a double play, the runner closest to scoring is called out in addition to the batter-runner. If interference is committed by a retired runner or by some other member of the offensive team, the runner who is most likely to have been put out will be called out.

Under Little League (LL), high school (NFHS) and college (NCAA) rules, if interference is committed by a runner with the effect of preventing a likely double play, regardless of his intent, the batter-runner will be called out in addition to the runner who committed the interference.

Also under NFHS rules only, all runners are required to attempt to avoid collisions. If a runner fails to do so, he is guilty of malicious contact, which is one kind of offensive interference. Malicious contact carries the additional penalty of ejection from the game. In contrast, in professional and higher amateur baseball, violent collisions can occur without any interference (or obstruction), especially when a fielder is receiving a thrown ball near a base where a runner is trying to reach. Any collision that occurs in this situation is not interference, because the fielder's action is in regard to a thrown ball. As long as such a runner's actions are related to his attempt to reach the base, he cannot be called for interference. The most common case of this is when a runner is attempting to score and the catcher has control of the ball. If the catcher is in the path between third base and home plate, the baserunner may strike the catcher with his body in an attempt to dislodge the ball from the catcher's hand and then reach home plate. This is usually attempted only when the play is close. When the catcher is set up and ready, the runner has little chance of knocking the ball away. Any such attempt presents a significant chance of injury to the baserunner, which has prompted the malicious contact rule to be used more often. In addition to the general subjective definition of offensive interference, it is also interference by specific rule when:

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