Baseball is one of the few sports in which spectators can have a physical influence on the outcome of the game. Because this potential exists, Major League Baseball created rules to govern any situation involving fan interference in a game. Fan interference has had some extraordinary effects on big games and big moments in baseball.
Because fans attending Major League Baseball games are allowed to keep balls that travel out of play, the likelihood that a spectator will reach out for an approaching baseball increases. According to MLB.com, fan interference occurs when a spectator goes onto the field or reaches over, under or through a barrier and touches a ball in play or interferes with a player. The two areas where this can occur are along either foul line and along the outfield fence.
Going Into the Stands
MLB.com also points out that if a player reaches into the stands in an attempt to catch a fly ball, any spectator whose presence or actions might prevent the player from catching the ball is not guilty of fan interference. Such a scenario occurs frequently because players will take any chance to record an out. The likelihood of a fan getting in their way depends largely on whether they're home or on the road. Home fans commonly move back to give one of their own players extra room to catch the ball.
The job of determining whether fan interference has occurred belongs to the umpire. In addition, as described on Hardball Times.com, umpires are also responsible for determining where base runners would have ended up had the fan not interfered -- and placing those men on the appropriate base. A player on first, for example, may get a quick trip to third base or all the way to home if a fan snatches away a ball heading toward the outfield fence, depending upon how an umpire gauges the situation.
Similar to the introduction of video replay in other sports, baseball decided to use this tool for a variety of calls, boundary violations among them, late in the 2008 season. While this option is available to umpires, they decide whether to engage the video replay. A manager or player's request to do so will not necessarily be honored, particularly if the umpire is confident in his call.