(a) He intervenes in a case of unfair play.
(b) A serious injury to a Player or Umpire occurs.
(c) He is satisfied that, for an adequate reason, the Striker is
not ready to receive the ball and makes no attempt to play it.
(d) The Bowler drops the ball accidentally before delivery, or
the ball does not leave his hand for any reason, other than in an
attempt to run out the Non-Striker.
See Law 24.5. (Bowler Attempting to Run Out Non-Striker Before Delivery).
(e) One or both bails fall from the Striker's wicket before he
receives delivery.
(f) He leaves his normal position for consultation.
(g) He is required to do so under
Laws 26.3. (Disallowance of Leg-Byes), etc.
3. The Ball Ceases to be Dead, when:-
(a) The Bowler starts his run up or bowling action.
(a) It strikes an Umpire (unless it lodges in his dress).
(b) The wicket is broken or struck down (unless a Batsman is out
thereby).
(c) An unsuccessful appeal is made.
(d) The wicket is broken accidentally either by the Bowler during
his delivery or by a Batsman in running.
(e) The Umpire has called "no ball" or "wide".
Notes
(a) Ball Finally Settled
Whether the ball is finally settled or not -- see 1 (a)
above -- must be a question for the Umpires alone to decide.
(b) Action on Call of "Dead Ball"
(i) If "dead ball" is called prior to the Striker receiving a
delivery the Bowler shall be allowed an additional ball.
(ii) If "dead ball" is called after the Striker receives a
delivery the Bowler shall not be allowed an additional ball, unless
a "no-ball" or "wide" has been called.
