Bowlers often swing the ball in the air or make the ball spin when it pitches on the wicket.

So if the ball strikes the batsman's pad, the umpire must assess how much the ball would have moved had it not struck the pad.

Would it have swung or spun enough to hit the stumps? Or would the ball have moved too much and missed the stumps completely?

However, if the ball hits the pad on the full - without pitching - then the umpire is not permitted to infer whether the ball would have moved after pitching.