Interference (baseball) - Umpire's Interference

It is umpire's interference when the umpire hinders a catcher's attempt to throw anywhere. In this case, if the catcher's direct throw retires a runner the play stands, if not, the ball is dead and all runners must return to their time of throw bases.

It is also umpire's interference when an umpire is struck by a fair batted ball before it touches or passes near an infielder other than the pitcher. This can occur either because an umpire is inside the diamond or because the ball crosses 1st or 3rd base in fair territory then hooks or slices foul into the umpire positioned just outside the line behind the bag. In this case, the ball is dead, the batter is awarded first base, and all other runners advance only if forced. A common example is when a batter hits a fair ball down the first base line so hard that the first base umpire can't avoid it. Even though the hit would have surely been a bases clearing double or triple without the interference, it is only a single and runners advance no more than one base. This happened in the 1989 All-Star Game when the Pittsburgh Pirates' Bobby Bonilla led off the 9th with a scorching grounder that would have been an easy double, but it hit First Base Umpire Bob Engel in the legs as he tried to jump out of the way. Instead of being in scoring position down 5–3, Bonilla was forced out at 2nd the next play and the game ended on a double play.