Infield fly rule
The infield fly rule is a rule in baseball intended to prevent infielders from intentionally dropping pop-ups in order to turn double plays (or triple plays). Without this rule, a defense could easily turn a pop fly into a double or triple play when there are fewer than two outs with runners at first and second base or when the bases are loaded. If the runners stay near their bases to tag up, the defense could let the ball drop, throw to third base and then to second (or home to third or home to third to second), for a force-out at each base. If any of the runners stray too far from their bases, the defense could catch the pop-up and double-off any runner that failed to tag up.
When the rule is invoked, the batter is out (and all force plays removed) regardless of whether the ball is caught, thus negating the possibility for multiple outs.
The rule 
The rule applies only when there are fewer than two outs, and there is a force play at third base (i.e., when there are runners at first and second base, or the bases are loaded). In these situations, if a fair fly ball is in play, and in the umpire's judgment it is catchable by an infielder with ordinary effort, the umpire shall call "infield fly" (or more often, "infield fly, batter's out"); the batter will be out regardless of whether the ball is actually caught in flight. Umpires typically raise the right arm straight up, index finger pointing up, to signal the rule is in effect.
If "infield fly" is called and the fly ball is caught, it is treated exactly as an ordinary fly ball; the batter is out, there is no force, and the runners must tag up. On the other hand, if "infield fly" is called and the ball lands fair without being caught, the batter is still out, and there is still no force, but the runners are not required to tag up. In either case, the ball is live, and the runners may advance on the play, at their own peril.
An infield fly may be declared by any umpire on the field.
"Umpire's judgement" 
The infield fly rule is a judgment call, as the rule states that "The judgment of the umpire must govern" and "is in no sense to be considered an appeal play". The rule also states that "Infield Fly" shall be declared immediately upon an umpire's determination that a batted ball has become an infield fly based on the criteria described above and is solely based on the umpire's discretion. Since different umpires may have different definitions of what constitutes "ordinary effort," the rule may be applied differently depending on the umpire and game conditions.
"Catchable by an infielder" 
Any fair fly ball that could be caught by an infielder with ordinary effort is covered by the rule, whether or not it's in the infield, and whether or not an infielder catches it, or even attempts to catch it. For example, if an infielder retreats to the outfield in an effort to catch a fly ball, the infield fly rule may be invoked because the ball could have been caught by the infielder. Similarly, infield fly may also be called if an outfielder runs into the infield to catch a fly ball, if it could have been caught by an infielder with ordinary effort. It may be helpful to think of it as the "infielder fly rule." Specifically, the rule states an infield fly call should be determined by "whether the ball could ordinarily have been handled by an infielder, not by some arbitrary limitation such as the grass, or the base lines. The umpire must rule also that a ball is an infield fly, even if handled by an outfielder, if, in the umpire's judgment, the ball could have been as easily handled by an infielder."
"Ordinary effort" 
Ordinary effort given all circumstances must exist for the infield fly rule to be invoked. Thus, weather, wind, lighting, positioning of the defense, and the abilities of the players involved in the play must be taken into account. An infield fly in a major league game, thus, might not be so in a junior high school game due to the ability of the players involved.
Foul balls 
If the fly ball is near the foul lines, the umpire is to declare "infield fly, if fair." If the ball is not caught and ends up foul (including if it lands fair and then rolls foul before passing first or third base without being touched by a fielder), the infield fly call is canceled, and the play is treated as an ordinary foul ball. In contrast, if the ball lands foul and then rolls fair before passing first or third base without being touched, the infield fly takes effect and the batter is out.
This rule was first introduced in 1895 by the National League in response to infielders' intentionally dropping pop-ups to get multiple outs by forcing out the runners on base, who were pinned near their bases while the ball was in the air. At that time, the rule only applied with one man out; the current rule came into effect in 1901. For example, with runners on first and second and fewer than two outs, a pop fly is hit to the third baseman. He intentionally allows the fly ball to drop, picks it up, touches third and then throws to second for a double play. Without the infield fly rule it would be an easy double play because both runners will stay near their bases while determining if the ball will be caught.
2008 World Series 
In the fifth game of the 2008 World Series between the Tampa Bay Rays and Philadelphia Phillies at Citizens Bank Park in Philadelphia, Pedro Feliz of the Phillies hit a pop-up to the right side of the infield with runners on first and second and one out, in strong rain and swirling winds, and the infield fly rule was not invoked. Umpiring crew chief Tim Tschida explained that "The infield fly rule requires the umpires' judgment to determine whether or not a ball can be caught with ordinary effort, and that includes wind" and that the umpire's determination was that in this case there was no infielder who could make the play with "ordinary effort."
2012 National League Wild Card Playoff 
In the eighth inning of the 2012 National League Wild Card Playoff between the St. Louis Cardinals and the Atlanta Braves, Andrelton Simmons of the Braves hit a pop-up into shallow left field with one out and men on first and second bases. Cardinals shortstop Pete Kozma, who was playing in normal position, ran out to left field to catch the ball while left fielder Matt Holliday, who was playing very deep in left, ran in to catch it as well. Although Kozma initially called to catch the ball, as the ball came down, he suddenly moved out of the way (apparently thinking Holliday was about to catch it), and the ball fell between himself and Holliday. While it initially appeared that Simmons (the batter) had safely reached first base and the Braves had the bases loaded with one out, Simmons was called out because left field umpire Sam Holbrook had called "infield fly" just before the ball hit the ground, and the Braves now had runners at second and third with two out, instead of bases loaded with one out. The Braves did not score in the inning, and the Cardinals went on to win the game, 6-3, eliminating the Braves from the postseason.
After the call, angry Braves fans began throwing plastic bottles and other debris onto the field, causing the game to be delayed for nearly 20 minutes. The game was played by the Braves under an official protest from their manager, but shortly after the game, Joe Torre, MLB executive vice president for baseball operations, denied the protest, citing umpire's judgment. Torre made the ruling immediately following the game (waiving the normal 24-hour review period) due to the importance of the game and the quick turnaround time before the next playoff game. The spot where the ball had landed was 225 feet from home plate. In the past three MLB seasons, there were six infield-fly rulings on balls that weren't caught, and the longest was measured at 178 feet, which is 47 feet less than the ball Simmons hit.
Runner on first base only 
The infield fly rule is not in effect if there is a runner on first only, as the rules-makers assumed fielders would not gain any significant advantage by forcing out the runner rather than the batter; in either case, the net result would be one more out and a runner on first base. Note that in this situation, it is possible for the defense to turn a double play after a dropped infield fly, though not likely. Assuming the batter makes an honest effort to reach first in a timely manner, the batter should beat out any attempt at a double play. Runners are protected by a separate rule (6.05l) from fielders intentionally dropping line drives (or any infield fly not covered under the infield fly rule) in order to turn double plays. See line drives section below.
Hit runners 
A runner hit by an infield fly while standing on a base is additionally protected from being declared out due to interference, unless this interference is deemed intentional (which appeared in the rules in 1940).
Runner advancement 
Just as for any other fly ball, if an infield fly is caught, runners must retouch (or "tag up") their time-of-pitch base before attempting to advance; if an infield fly is not properly caught, no tag up is required and the runners may advance at their own risk, as with the batter being declared out, the force on preceding runners is removed. From the runners' perspective, the situation is no different from any fly ball. They must tag up if the ball is caught, and free to advance without tagging if the ball is dropped. One source of confusion is the wording of the rule where it states the runners may advance "...after the ball is touched...". This could be misinterpreted as the runner must tag up after the ball is touched even if the ball is ultimately dropped. The intention of the wording is to prevent an awkward situation for the runner in the event the fielder is juggling or bobbling the ball, either intentionally or not, before gaining full control. A runner standing on the base may advance the moment a fielder touches a fly ball regardless of whether the ball is ultimately caught or dropped. That the ball is live in any case after the infield fly rule is invoked is significantly different from the intentional drop rule (6.05l), where under that rule, the batter is out, the ball is dead and all runners must return to their original bases.
Line drives 
The infield fly rule cannot be invoked on line drives (added to the rules in 1904) or bunts (added in 1920); The infield fly rule additionally does not pertain to all situations in which the defense may wish to allow a fly ball to drop uncaught. For example, with just a runner on first, an alert infielder might intentionally allow a pop-up to drop to the ground and get the force at second, if it happens that the runner on first is faster afoot than the batter-runner is, or if the batter is loafing on his way to first base. This is only legal if the fielder lets the ball hit the ground untouched, which carries some risk to the fielder as it might bounce away from him. However, in all situations where the infield fly rule does not apply, a different rule (6.05l) prevents fielders from touching a catchable ball and dropping it intentionally in an attempt to turn a double or triple play (in such cases, the batter is out and the ball is dead; no runner may advance). This rule is called the intentional drop rule and is overridden by the infield fly rule, when applicable.
Batter passing another runner 
Even without the infield fly rule, it is occasionally possible that clever play by a batting team with a runner on first base (and possibly second or third) can avoid a double or triple play and in fact ensure that the result is exactly the same as if the Infield Fly rule were in effect. This is true under any circumstance whereby the batter is able to overtake a baserunner before a force play is executed, even when the bases are loaded. The batter can run to first base and stand there while all other baserunners stay where they are (including the one at first base, so that both the first base runner and the batter are standing on first base). If the fielder allows the ball to drop, then the moment the ball touches the ground, the batter can advance toward second base, passing the first base runner and causing himself, the batter, to be called out according to rule 7.08h. According to rule 7.08c, this nullifies the force so that all the baserunners can stay where they are, and will leave the bases loaded if they were already loaded when the batter came to the plate.
In practice, however, in professional baseball and other adult and teen leagues infield flies are usually caught (or occasionally dropped) before the batter can reach first base. In children's leagues, with a shorter distance between home plate and first base, a fast running batter can sometimes reach first base before a high infield fly is playable by the infield. Also, in some little leagues the infield fly rule is not in effect, allowing fielders to take advantage of the batting team as described above.
The infield fly rule and legal theory 
The infield fly rule was the subject of an article in U.S. legal history. William S. Stevens was a law student in 1975 when he anonymously published “The Common Law Origins of the Infield Fly Rule” in the University of Pennsylvania Law Review. The article was humorous but also insightful on how common law related to codified regulation of behavior. It has been cited in numerous legal decisions and in subsequent literature.
Potential unassisted, untouched, triple play 
Among the many unlikely and bizarre scenarios that involve the Infield Fly Rule, in the April 6, 2009 issue of Newsweek, George Will has postulated an "Unassisted, Untouched" Triple Play. In this scenario, there are runners on first and second and no outs. The Infield Fly Rule is invoked so the batter is out. The runner on first base advances to second and continues, passing the runner on second, making the runner from first base automatically out. Finally, the pop-up drops and hits the runner who was on second base after he leaves the base (if he is standing on the base during an infield fly and the ball hits him, he is not out, but the ball becomes dead and the play is over), making this the third out. All of this happens without a single defensive player touching the ball.
The bizarre twist to this is how it would be scored. In the case of an infield fly rule, the official scorer decides which fielder was most likely to have caught the ball, and assigns the first out to that player. The out for passing a runner is assigned to the closest fielder, as is the third out for being hit by the ball. It is quite possible in such a scenario that the same fielder would be given credit for all three outs, most likely the shortstop or second baseman.
An unassisted triple play involving the infield fly rule occurred during an NCAA game between the BYU Cougars and the SDSU Aztecs in May 2011. Runners on first and second advanced without noting the infield fly call and were tagged out by BYU shortstop Andrew Law.
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- E.g., "The Contribution of the Infield Fly Rule to Western Civilization (and vice versa)," Anthony D'Amato, Northwestern University Law Review, Vol. 100, No. 1 (2005)
- "Rare triple play helps BYU end SDSU baseball season". San Diego Union Tribune. May 2011. Retrieved 2011-05-27.