During the bowling of a ball, one umpire stands behind the non-striker's wicket, ready to make judgements on LBWs and other events requiring a decision. The other umpire stands on the striker's popping crease, about 20 metres (20 yards) to one side (usually the leg side, but not always), ready to judge stumpings and run-outs at his end. The umpires remain at their respective ends of the pitch, thus swapping roles every over. The umpires swap ends after each side has completed one innings.
Whenever any decision involving the fall of a wicket is in any doubt whatsoever in an umpire's mind, the umpire must rule in favour of the batsman.
If a live ball hits an umpire, it is still live and play continues. If it lodges in an umpire's clothing, it becomes dead.
Some cases, such as very fine edges of the ball off the bat caught by the wicketkeeper, or all LBWs, are not obvious. In such cases, the umpire does not make a decision unless the fielding team appeal to the umpire for a decision. This is conventionally in the form of the question "How's that?" - often shouted with enthusiasm by multiple members of the fielding team as "Howzat?!"
Following an appeal, the umpire will make a decision and all players must abide by it.
The type of events that may be referred to the third umpire are explicitly restricted, and the list is updated from
time to time following administrative reviews. Currently, only the following events may be referred to the third umpire:
Extra Detail: Umpires Signals
The umpires signal various events with gestures, as follows:
Extra Detail: Third Umpire
If the technology is available for a given match, a third umpire may be used. He sits off the field, with a
television replay monitor. If an on-field umpire is unsure of a decision concerning certain events, he may signal
for the third umpire to view a television replay. The third umpire views a replay, in slow motion if necessary, until
he either reaches a decision or decides that he cannot make a clear decision. He signals the result to the on-field
umpire, who must then abide by it. If the equipment fails, the third umpire signals no decision.
Extra Detail: Match Referee
Professional level cricket matches are presided over by a match referee,
who watches from outside the field. The referee makes no decisions of relevance to the outcome of the game, but
determines penalties for breaches of various rules and misconduct. In professional games, these penalties are
monetary fines and/or suspension from subsequent matches.
The type of events that may be referred to the third umpire are explicitly restricted, and the list is updated from time to time following administrative reviews. Currently, only the following events may be referred to the third umpire: