An umpire is a person who has the authority to make judgements on the cricket field, according to the Laws of Cricket. Besides making decisions about legality of delivery, appeals for wickets and general conduct of the game in a legal manner, the umpire also keeps a record of the deliveries and announces the completion of an over.
When a ball is being bowled, one umpire (the bowler's end umpire) stands behind the stumps at the non-striker's end (that is, the end from which the ball is being bowled), which gives him a view straight down the pitch. The second (the striker's end umpire) takes the position that he feels gives him the best view of the play. Through long tradition, this is usually square leg, in line with the popping crease and a few yards to the batsman's leg side, hence he is sometimes known as the square leg umpire. However, if a fielder takes up position at square leg or somewhere so as to block his view, or if there is an injured batsman with a runner, then the umpire must move somewhere else, typically either a short distance or to point on the opposite side of the batsman. If the square-leg umpire elects to stand at point, he is required to inform both the batsmen, the captain of the fielding team, and his colleague. He may also move to the point position later in the afternoon if the setting sun prevents a clear view of the popping crease at his end. It is up to the umpires to keep out of the way of both the ball and the players. In particular, if the ball is hit and the players attempt a run, then the umpire behind the stumps will generally retreat to the side, in case the fielding side attempts a run out at that end.
At the end of each over, the two umpires will exchange roles. Because the bowlers end alternates between overs, this means they only move a short distance.
During play, the umpire at the bowler's end makes the decisions, which he mainly indicates using arm movements. Some decisions must be instantaneous, whereas for others he may pause to think or discuss it with the square leg umpire, especially if the latter may have had a better view. Scorers are required to acknowledge the signals from umpires; and umpires are required to get an acknowledgement before allowing the match to proceed.
An umpire will not give a batsman out unless an appeal is made by the fielding side, though a batsman may walk if he knows himself to be out. If the fielding side believes a batsman is out, the fielding side must appeal, by asking "How's that?" or "How was he?" (or by any other means that either umpire deems as a method of appealing). The umpire's response is either to raise his index finger above his head to indicate that the batsman is out, or to clearly say "not out", which is usually accompanied with a shake of the head. The 'out' signal is the only signal that the scorer does not have to acknowledge.
A batsman may be out in numerous ways:
An umpire will signal a dead ball by holding one arm out horizontally and shout "no ball". The no ball doesn't count as one of the six in the over, and severely reduces the ways in which a batsman may be out, with the most common forms of dismissal all being removed, except for run out. The batsman may attempt to score runs from the no ball.
No balls occur in numerous ways:
A wide ball is the term used to describe a delivery which is too wide or too high to be hit by the batsman. A wide is signalled by extending both arms out horizontally and is accompanied by a call of wide ball. It does not count in the over, and again reduces the way in which a batsman can be out. If a delivery satisfies the criteria for both a no ball and a wide, the call and penalty of no ball will take precedent.
Normally, if the ball passes the batsman without being deflected, the wicketkeeper will catch it. This normally prevents the scoring of runs because the batsmen will be unable to complete a run before being stumped or run out by the wicketkeeper. However, if the wicketkeeper fumbles or misses the ball, the batsmen may be able to score runs safely, and may choose to do so. The number of runs scored are scored as byes. They are added to the team's total, but not to the number of runs scored by either batsman and will not be considered as runs conceded by the bowler. If runs are to be scored as byes, the umpire will hold up one open palm above the head.
If the ball deflects off the batsman's body and needs to be gathered by a fielder, the batsmen may have the opportunity to score runs safely, and may choose to do so. The number of runs scored are scored as leg byes. They are added to the team's total, but not to the number of runs scored by batsman and will not be considered as runs conceded by the bowler. Leg byes are signalled by the umpire touching a raised knee.
An umpire will, in certain circumstances (first five points below), signal a dead ball by crossing and uncrossing his wrists below his waist with the call “dead ball”.
Dead balls occur in numerous ways:
If one of the batsman turns to complete runs after the first without grounding his person or equipment behind the popping crease, then a short run is signalled by the umpire tapping his near shoulder with his fingers and the short runs are not scored. If more than one run is short, the umpire will inform the scorers as to the number of runs scored.
For extreme misconduct by one team, the umpire may award five penalty runs to the other team. Placing one arm on the opposite shoulder indicates that the penalty run are awarded to the fielding team, but if the umpire taps that shoulder, the penalties are awarded to the batting team.
Five penalty runs are more commonly awarded when the ball strikes a foreign object on the field, usually a helmet of the fielding side.
If the umpire makes an incorrect signal, he may revoke it. To do so, he crosses his arms across his chest, then makes the corrected signal. A revocation may be made if the umpire discovers an incorrect application of the laws, such as, signalling "out" before realising that the other umpire signalled a no-ball. Also, an umpire may revoke if he accidentally signals a four though he intended to signal six.
If a batsman scores four by hitting the ball across the boundary (not by actually running them), the umpire signals by waving his arm back and forth in front of the chest.
If a batsman scores six by hitting the ball across the boundary (not by actually running them), the umpire signals by raising both hands above his head.