Dead ball

The ball comes into play at the moment a bowler starts his run-up or, in the very rare instance of a bowler not employing a run-up, his bowling action.

It remains in play until it is clear to the bowler's end umpire that neither the fielding side nor the batsmen still regard it as being in play; very often this is when it has finally settled in the hands of the wicket-keeper or is on its way back to the bowler. At that point it becomes a dead ball. Although the fielders can still appeal for anything that took place before the ball became dead, once it has done so then no further action can be taken that could result in a dismissal and no runs can be scored.
There are several other ways in which the ball automatically becomes dead, including when ...
  • a boundary is scored
  • a batsman is dismissed
  • Lost ball is called by the fielding side
  • the umpire calls Over, Time
  • the umpire awards Penalty runs for a player returning to the field without permission and coming into contact with the ball
  • the umpire awards Penalty runs for certain acts of illegal fielding
  • the ball hits a fielder's helmet parked on the ground behind the wicket-keeper
  • the ball becomes trapped, even momentarily, between a batsman's bat and his body or is trapped or lodges in his clothing or other equipment
  • the ball lodges in an umpire's clothing or in a helmet being worn by a fielder
There are a number of occasions on which the umpire should call and signal Dead ball in order to bring play to a stop. He should do so whenever he leaves his normal position to consult with his colleague, or if a player or umpire is seriously injured, or if he has to intervene in a case of unfair play such as the umpire awards Penalty runs for deliberate attempts to distract the striker while he is receiving or preparing to receive the ball, or to distract or obstruct either batsman after the ball has been received.
There are less dramatic reasons, too, for the ball to be declared dead. A bail may fall from the striker's wicket before the delivery arrives, the striker might have been distracted by a noise or movement while he was waiting to receive the ball - perhaps somebody suddenly walked in front of the sightscreen, right through his line of vision, the bowler may drop the ball by accident, or perhaps fail to let go of it at all.
As far as whether a dead ball counts in the over, the rule is that the delivery does not count as one of the over if the striker did not have an opportunity to play it, but does count if he did, providing, of course, that it wasn't also a No ball or a Wide.
Like all rules there are exceptions that can occur after the ball has been received and that ensure that the delivery does not count in the over. Some recent ones include a player returning to the field without permission and coming into contact with the ball, many cases of illegal fielding and distraction or obstruction of batsmen.