I've seen a lot of Twitter comments since The Un-Catch along the lines of, "The rule is clear. That was fan interference. Martinez should've been out." So now, let us consider the rule book, and then take another look at the play to see how clear cut this really is. (And at your leisure, take a look at other plays — lots of other plays — where the interference issue has come up.)
First look at Rule 2.00, which defines spectator interference as occurring "when a spectator reaches out of the stands, or goes on the playing field, and touches a live ball." Then check out Rule 3.16, a meatier discussion of what spectator interference looks like in practice:
When there is spectator interference with any thrown or batted ball, the ball shall be dead at the moment of interference and the umpire shall impose such penalties as in his opinion will nullify the act of interference.
APPROVED RULING: If spectator interference clearly prevents a fielder from catching a fly ball, the umpire shall declare the batter out.
Rule 3.16 Comment: There is a difference between a ball which has been thrown or batted into the stands, touching a spectator thereby being out of play even though it rebounds onto the field and a spectator going onto the field or reaching over, under or through a barrier and touching a ball in play or touching or otherwise interfering with a player. In the latter case it is clearly intentional and shall be dealt with as intentional interference as in Rule 3.15. Batter and runners shall be placed where in the umpire’s judgment they would have been had the interference not occurred. No interference shall be allowed when a fielder reaches over a fence, railing, rope or into a stand to catch a ball. He does so at his own risk. However, should a spectator reach out on the playing field side of such fence, railing or rope, and plainly prevent the fielder from catching the ball, then the batsman should be called out for the spectator’s interference. Example: Runner on third base, one out and a batter hits a fly ball deep to the outfield (fair or foul). Spectator clearly interferes with the outfielder attempting to catch the fly ball. Umpire calls the batter out for spectator interference. Ball is dead at the time of the call. Umpire decides that because of the distance the ball was hit, the runner on third base would have scored after the catch if the fielder had caught the ball which was interfered with, therefore, the runner is permitted to score. This might not be the case if such fly ball was interfered with a short distance from home plate.
So now, take a look at that video again. Then go back to the rule: "If spectator interference clearly prevents a fielder from catching a fly ball, the umpire shall declare the batter out." And: "No interference shall be allowed when a fielder reaches over a fence, railing, rope or into a stand to catch a ball. He does so at his own risk. However, should a spectator reach out on the playing field side of such fence, railing or rope, and plainly prevent the fielder from catching the ball, then the batsman should be called out for the spectator’s interference."
It's pretty clear the fan reached across the barrier to fumble with the ball. He clearly ended any chance Reddick had to catch it. Listen to the broadcasters viewing the replays, and they seem to be leaning toward the obvious: the clumsy Detroiter had interfered with the ball.
But when looking for certainty in baseball, religion or law, always beware of adjectives, adverbs and other conditional language that creates miles of room for interpretation. In the rule, the spectator must "clearly" or "plainly" prevent a catch. So — did the fan obviously stop Reddick from making the catch? I watch the trajectory of that little white orb descending toward the stands, and I honestly can't tell.
The play came down, as it often does, to an umpiring decision. They might have gotten it wrong. It wouldn't be the first time.