when does the law of LBW(leg before wicket)in cricket come into excistance?

Answer 1

The basic rules of cricket such as bat and ball, the wicket, pitch dimensions, overs, how out, etc. have existed since time immemorial. In 1727

In 1744, the Laws of Cricket were codified for the first time and then amended in 1774, when innovations such as lbw, middle stump and maximum bat width were added.

Answer 2

In the early 20th century so many runs were being scored that debate ensued on reforming the “leg-before-wicket” law, which had been introduced in the 1774 laws to prohibit a batsman from using his body to prevent the ball from hitting his wicket.

The batsman is out “leg before wicket” (lbw) if he intercepts with any part of his person (except his hand) that is in line between wicket and wicket a ball that has not first touched his bat or his hand and that has or would have pitched (hit the ground) in a straight line between the wickets or on the off side provided the ball would have hit the wicket.

Answer 3

i suppose u r asking that how exactly is a person ruled out using the LBW rule. that can be explained as follows:

An umpire will rule a batsman out LBW underseries of circumstances that primarily include the ball striking the batsman's body (usually the leg) when it would otherwise have continued to hit the wicket.The rule is designed to prevent a batsman simply using his body to prevent the ball from hitting the wicket (and so avoid being bowled out) rather than using his bat to do so. The rule applies if the ball hits the batsman on any part of his body, except for the glove of a hand in contact with the bat (which is considered part of the bat).