Is a fielder allowed to change position during the bowler's run up?

Question

If a fielder standing in the gully position moves to cover point (as bowler starts his run up) before the batsman plays the ball what action will the umpire want to take? Often a fielder will move forward or backward, but in this situation the fielder standing in gully moved to cover point before the batsman faced the ball.

He checked the ground fielding positions before facing and at that time the fielder was in the gully position, then suddenly he was at cover point and took a catch. What is the reply by the umpire?

Answer 1

This is a dead ball. Law 20.5 makes it clear when the ball is in play:

The ball ceases to be dead – that is, it comes into play – when the bowler starts his/her run-up

Law 28.6 defines the allowable movement by fielders once the ball is in play:

28.6.1 Any movement by any fielder, excluding the wicket-keeper, after the ball comes into play and before the ball reaches the striker, is unfair except for the following:

[ some exceptions which don't apply here ]

[ ... ]

28.6.3 In the event of such unfair movement, either umpire shall call and signal Dead ball.

If the movement was a deliberate attempt to distract the striker, it would be covered by Law 41.4 and result in penalty runs.