LBW or leg before wicket is one of the methods in which a batsman can be dismissed in cricket. The basis of the rule is that a batsman is out if the ball hits his legs first, which could have otherwise gone on to hit the stumps. However, this rule is not as straightforward as it seems and has a history of over two centuries.
A brief history
Up untill the mid-1930s, the LBW law was such, that the batsman can be given out LBW only if the ball is pitching in line with the stumps. So irrespective of whether the ball would have gone on to hit the stumps, if it pitched outside the line of the off-stump or leg-stump, the batsman was not out. This rule allowed the batsman to simply pad away the ball in a defensive way if the ball was not in line with the stumps. To counter this rule, bowlers resorted to bowling bouncers. This made it difficult for the batsman to score runs and survive on the crease. Hence, in 1935, a revised version of LBW came into effect. According to it, if the ball is pitching outside the off-stump, hits the pad, and would have gone on to hit the stumps, the batsman is out. However, if the ball pitched outside the leg-stump, the batsman is not out. This rule stands even today.
A few explanations have been proposed as to why pitching outside the leg in a LBW appeal is not out. Firstly, a batsman, whether right-handed or left-handed, has a wider range of shots that he or she can hit by swinging his bat from off-side to leg-side rather than the other way round. Secondly, if a bowler bowls from the leg-side, he will face the batsman’s legs first and not the bat itself. This is in contrast to when the bowler bowls from the off-side, where he faces tbe bat first. Cricket is a game between bat and ball, and it makes sense, as to why a ball pitching outside the off-stump can be legally counted for a LBW dismissal. Moreover, bowling outside the leg-stump is called a negative line because it makes it difficult for the batsman to hit the shots.
A final technical explanation that justifies this law can be explained through the blind spot rule which everyone can try at home. Stand in your normal batting stance facing the bowler. Now without moving your head and neck, move your eyes towards the off-side. This is relatively easy as you can certainly appreciate the fielders in that area. Now try doing the same by moving both your eyes towards the leg-side. Clearly, one cannot have a good view of the field and a blind spot develops. Thus, if a bowler is to bowl outside the leg stump, with the goal of a possible LBW, it would be a highly partial law in the bowler’s favour.
The above explanations justify the modern law. But the way the shorter formats (like T10 and T20) cricket has forced the batsmen to increase their range of shots, do not be surprised if further modificafions are to come in the LBW law.