The Dead Ball law is the most important law in cricket by a large distance. It shapes everything else. It contains instructions for when the ball is in play and when it isn’t. It basically tells us when the delivery begins and ends. Further, it provides a chronology of the actions which can cause a play to end. In doing so, it provides markers for actions which are considered significant. Further, the Dead Ball law also specifies the circumstances in which a replay of the delivery is necessary. Under the Dead Ball law, there are four significant events in any delivery:
1. The bowler starts his run up and the ball ceases to be Dead.
2. The bowler delivers the ball (this is the point of no return the batsman cannot withdraw from the delivery)
3. The batsman plays the ball. This can result either in runs (0 or more) or dismissal.
4 (a). The fielder fields the ball and returns it to the keeper (this can result in dismissal, it is significant to the question of whether or not a run is considered to be “in progress” - see Law 18, and finally, it determines whether the ball is “finally settled in the hands of the wicket-keeper or of the bowler” there by making it Dead again. - see Law 20.1).
4 (b). The ball crosses the boundary (see Law 19).
At each of these stages, the play can come to an end and the ball can be ruled dead. The consequence of the ball being dead (something which the umpire decides) is that all actions after this are void. So if the bowler pulls out of the run up or the batsman backs away from receiving the delivery, the ball is ruled dead (this is significant because the batsman cannot be run out from this delivery because the delivery is over, the ball is Dead). If a fielder distracts the striker as the bowler is delivering the ball, then the umpire can declare the ball dead and this is also one of the circumstances in which the ball has to be re-bowled. And so on.
Under DRS, the player can review an LBW or Caught dismissal (which occurs at 3 above). If an Out decision is reversed, then all applicable actions prior to (3) are reinstated. If a not out decision is reversed, then all actions prior to (4) are reinstated. The basic principle is that the ball which is dead cannot be retrospectively brought alive. If a DRS review requested by a batsman finds that the bowler has overstepped, then the Out decision by the umpire is void - no dismissal other than a run out is possible. This reverses the dismissal. It does not bring back to life any runs completed by the batsmen because those occur after the ball is already Dead. But it does give the batting side the run for the no-ball because the no-ball occurred at (2) above, before the LBW or Caught which occurred at (3). This is an elegant idea. [3.7 of the DRS rules1]
The furore over Rishabh Pant being apparently denied 4 runs is just one example of how poorly this law is understood. Pant was not denied 4 runs, because he did not score a boundary. The ball was dead when he was given out. It would be possible to rewrite the Dead Ball law, but doing so would inescapably involve one of two things: (a) breaking the principle of never retrospectively turning a dead ball into a live ball and creating a mind-boggling range of contradictions, or (b) changing the basic logical structure of the sport to account for the possibility of double plays and other things. Further, there is no reason to think that a new logical structure will not contain its own problems.
If you really want to understand how cricket is designed, read the Dead Ball law. It is the engine room of the game.
3.7 of the DRS rules (titled “Dead Ball”) specifically address what happens to the Dead Ball law under DRS.
3.7.1 If following a Player Review request, an original decision of Out is changed to Not out, then the ball is still deemed to have become dead when the original decision was made (as per clause 184.108.40.206). The batting side, while benefiting from the reversal of the dismissal, shall not benefit from any runs that may subsequently have accrued from the delivery had the on-field umpire originally made a Not out decision, other than any No ball penalty that could arise under paragraph 3.3.5 above.
3.7.2 If an original decision of Not out is changed to Out, the ball shall retrospectively be deemed to have become dead from the moment of the dismissal event. All subsequent events, including any runs scored, shall be ignored.