The third umpire, often known as the TV umpire, is an off-field umpire who makes decisions when the on-field umpires are undecided. The third umpire is off the field, watching a television replay. When there is time before the next play, the third umpire will signal either "yes" or "no" to indicate his decision. If he signals "yes," then the original call stands; if he signals "no," then the opposite decision must be made.
The third umpire is used in cricket because of its large number of decisions that need to be made in one day's play. On average, each ball in cricket requires three calls: one from the on-field umpires and two from the third umpire. This means that a single day's play in cricket needs at least six umpires on the field: three on-field umpires and three third umpires. However, since some decisions can be decided upon by mutual agreement between the on-field umpires or their referees, not all games require this many umpires. A total of 56 such agreements have been recorded since the advent of television technology.
In most cases, players and spectators see only the on-field umpires' decisions and do not know what role the third umpire has played in making those decisions.
The third umpire (sometimes known as the TV umpire) is an off-field umpire who is utilized in some cricket matches, notably international matches. Their responsibility is to make the ultimate decision on matters submitted to them by the two on-field umpires or the players. If necessary, the third umpire can also serve as an emergency on-field umpire.
In most cases, the third umpire will not have a significant impact on game play and will not affect the outcome of any match. However, they do have some influence over certain incidents during a game. For example: if there is doubt about whether a ball has crossed the line boundary, then the third umpire can put their mark on it to determine this fact before they sign off on the state of the game.
Some countries also use guest umpires for one-day matches. These are usually former international level cricketers who are hired by the board to provide advice to the on-field umpires.
In many ways, the role of the third umpire is similar to that of a reserve fielder in baseball or a replacement player in basketball. Both parties try to find extra support beyond what is required on the field during important moments of the game.
There are several methods used by boards to appoint third umpires. They may be assigned by their country's governing body for international sports (such as the ICC), or they may be selected by the boards themselves.
They work in collaboration with the other two umpires.
They have the power to rule on any point that involves judgment rather than just rules. For example, they can rule on whether a ball was hit into the stands or not. They can also rule on whether a player has been hit by a ball even if it isn't clear where it went after it was hit. The only time they cannot rule is if there is video evidence that clearly shows what happened on the field. In this case, they would send a note to the on-field referees explaining their decision and asking them to proceed accordingly.
They can also rule on whether a player has been distracted from his job while he was not wearing a helmet. They will always ask for proof that the player had taken his eye off the ball but if no proof is provided, then he would be called out for not wearing a helmet.
The third umpire can change or resolve any dispute that the on-field umpires are unable to reach a conclusion on.