The ICC has come up with a revised set of guidelines for the way the 2.5m rule in the UDRS will be interpreted that says umpires must also consider the distance between the ball pitching and point of impact. On Sunday, they announced a tweak in the guidelines, allowing on-field umpires to reverse not-out decisions if the replays showed part of the ball to be hitting middle stump, even if the batsman was hit more than 2.5m away. They have now issued a full release about the guidelines umpires will use in the World Cup. 

When a not-out lbw decision is reviewed, and the replay shows the ball has made impact more than 2.5m away from the wickets, the umpires also have to consider another factor: the distance the ball has travelled between pitching and hitting the pad. If that distance is less than 40cm, and the ball still has to travel more than 2.5m to reach the stumps, then, it has been decided, any not-out decision given by the on-field umpire will remain not out. 

It has also been decided that if the batsman is more than 3.5m down the wicket, then again not-out decisions will not be overturned. The only scenario in which an lbw decision will be reversed in favour of the bowler if the batsman is more than 2.5m away from the wicket is if the distance is less than 3.5m and the distance between pitching and point of impact is more than 40cm. In that case, some part of the ball must be hitting middle stump, and the whole ball must be hitting the stumps below the bails. 

In essence, the new guidelines will allow umpires to reverse decisions where the batsman is plumb and there is no doubt the ball would have hit the stumps, even if the impact is far down the wicket. The reason the 40cm distance is important is because Hawk Eye needs to monitor the ball's movement for some distance after it has pitched in order to determine where it would have gone after hitting the pad. If a batsman is struck very soon after the ball has bounced, then the accuracy of the prediction as to where the ball would have moved afterwards is not as high. 

In cases where the original decision is out, the 2.5m or 40cm distances do not come into play, as in that situation Hawk Eye must show the ball to be completely missing the stumps in order for the umpire to reverse his decision.