In case of unintentional interference with play by any person herein authorized to be on the playing field (except members of the team at bat who are participating in the game, or a base coach, any of whom interfere with a fielder attempting to field a batted or thrown ball; or an umpire) the ball is alive and in play. If the interference is intentional, the ball shall be dead at the moment of the interference and the umpire shall impose such penalties as in his opinion will nullify the act of interference.
Rule 6.01(d) Comment (Rule 3.15 Comment): For interference with a fielder attempting to field a batted or thrown ball by members of the team at bat or base coaches, who are excepted in Rule 6.01(d) (Rule 3.15), see Rule 6.01(b) (Rule 7.11). See also Rules 5.06(c)(2), 5.06(c)(6) and 5.05(b)(4) (Rules 5.09 (b)), 5.09(f) and 6.08(d)), which cover interference by an umpire, and Rule 5.09(b)(3) (Rule 7.08(b)), which covers interference by a runner.
The question of intentional or unintentional interference shall be decided on the basis of the person’s action. For example: a bat boy, ball attendant, policeman, etc., who tries to avoid being touched by a thrown or batted ball but still is touched by the ball would be involved in unintentional interference. If, however, he kicks the ball or picks it up or pushes it, that is considered intentional interference, regardless of what his thought may have been.
PLAY: Batter hits ball to shortstop, who fields ball but throws wild past first baseman. The coach at first base, to avoid being hit by the ball, falls to the ground and the first baseman on his way to retrieve the wild thrown ball, runs into the coach. The batter-runner finally ends up on third base. Whether the umpire should call interference on the part of the coach is up to the judgment of the umpire and if the umpire felt that the coach did all he could to avoid interfering with the play, no interference need be called. If, in the judgment of the umpire, the coach was attempting to make it appear that he was trying not to interfere, the umpire should rule interference.