thumb|right|A 1904 illustration from the [[Badminton Library's Cricket, showing a batsman who is leg before wicket. The original caption was "A clear case" [of lbw].|alt=Drawing of a batsman hit on the pads by the ball. The wicketkeeper is about to appeal.]]
Leg before wicket (lbw) is one of the ways in which a batter can be dismissed in the sport of cricket. Following an appeal by the fielding side, the umpire may rule a batter out LBW if the ball would have struck the wicket but was instead intercepted by any part of the batsman's body (except the hand(s) holding the bat). The umpire's decision will depend on a number of criteria, including where the ball pitched, whether the ball hit in line with the wickets, the ball's expected future trajectory after hitting the batsman, and whether the batsman was attempting to hit the ball.
Leg before wicket first appeared in the laws of cricket in 1774, as batsmen began to use their pads to prevent the ball from hitting their wicket. Over several years, refinements were made to clarify where the ball should pitch and to remove the element of interpreting the batsman's intentions. The 1839 version of the law used a wording that remained in place for nearly 100 years. However, starting in the latter part of the 19th century, batsmen became increasingly expert at "pad-play" to reduce the risk of their dismissal. Following a number of failed proposals for reform, in 1935 the law was expanded, such that batters could be dismissed lbw even if the ball pitched outside the line of off stump. Critics felt this change made the game unattractive as it encouraged negative tactics at the expense of leg spin bowling.
After considerable debate and various experiments, the law was changed again in 1972. In an attempt to reduce pad-play, the new version, which is still in use, allowed batters to be out lbw in some circumstances if they did not attempt to hit the ball with their bat. Since the 1990s, the availability of television replays and, later, ball-tracking technology to assist umpires has increased the percentage of lbws in major matches. However, the accuracy of the technology and the consequences of its use remain controversial.
In his 1995 survey of cricket laws, Gerald Brodribb states: "No dismissal has produced so much argument as lbw; it has caused trouble from its earliest days".
Definition
thumb|left|upright|The area shaded in blue in the above diagram of a cricket pitch is in line with the wickets
The definition of leg before wicket (lbw) is currently Law 36 in the Laws of Cricket, written by the Marylebone Cricket Club (MCC). If the bowler delivers a no-ball — an illegal delivery — the batter cannot be out lbw under any circumstances. Otherwise, for the batter to be adjudged lbw, the ball, if it bounces, must pitch in line with or on the off side of the wickets. Then the ball must strike part of the batter's body without first touching his/her bat, in line with the wickets and have been going on to hit the stumps. The batter may also be out lbw if, having made no attempt to hit the ball with their bat, they are struck outside the line of off stump by a ball that would have hit the wickets. The umpire must assume that the ball would have continued on the same trajectory after striking the batter, even if it would have bounced before hitting the stumps.
A batter can be out lbw even if the ball did not hit their leg: for example, a batter struck on the head could be lbw, although this situation is extremely rare. However, the batter cannot be lbw if the ball pitches on the leg side of the stumps ("outside leg stump"),