The third umpire (or TV Umpire) is an off-field umpire in international cricket matches who makes the final decision in questions referred to him by the two on-field umpires. Television replays and other technology are available to the third umpire to assist him in coming to a decision. An on-field umpire can, at his own discretion, use a radio link to refer any close decision concerning dismissals (catches, runouts or stumpings) or boundaries to the third umpire. Also players can initiate reviews of particular decisions by the on-field umpires, which are judged by the third umpire.
The third umpire was conceptualized by former Sri Lankan domestic cricketer, and current cricket writer Mahinda Wijesinghe and debuted in Test cricket in November 1992 at Kingsmead, Durban for the South Africa vs. India series. Karl Liebenberg was the third umpire with Cyril Mitchley the on-field umpire, referring the run-out decision in this match. Sachin Tendulkar became the first batsman to be dismissed (run out) by using television replays in the second day of the Test scoring 11.
Decision requests by the on-field umpires
In many cases of run out or stumped, the event occurs in a fraction of a second. If the on-field umpires are unable to decide if the batsman is out, they may request the third umpire to ascertain whether the batsman had made it home. The third umpire then looks at various TV replays from different angles, comes to a conclusion, and indicates his decision by pressing the appropriate signal. Originally decisions were conveyed in traffic light style (a red light indicating a batsman's dismissal, a green light not out); it is now common practice to display the decision via the large screen scoreboard, if available. If the umpire is unsure if a batsman is out or not, due to lack of conclusive evidence, the usual procedure is to acquit the batsman, known in cricketing parlance as "the benefit of the doubt".
The third umpire may also be called upon if the on-field umpire cannot decide which batsman is out (i.e. they end up at the same end). An example of this was the Third Test between New Zealand and the West Indies in 2006.
A batsman is caught out if a fielder catches the ball on the fly. In some cases the fielder may catch the ball a few inches above ground level. If the umpire's vision is obscured or is unsure if the ball bounced before the fielder caught the ball, he can also refer the decision.
A six is scored if the batsman hits the ball directly beyond the perimeter of the field. In some cases the ball may bounce just a foot inside the boundary rope resulting in four runs. If the umpire needs to ascertain if it had been a 4 or a 6, he may consult the third umpire. Near the boundary, often a fielder may dive to save the ball from travelling beyond the boundary. If the fielder makes any simultaneous contact with the boundary and the cricket ball, 6 runs are declared. A third umpire may also be consulted in such a case.
Decision requests by the players
The third umpire also adjudicates appeals initiated by the players against decisions made by the on-field umpires, as part of the Umpire Decision Review System, and reports to the on-field umpire whether his analysis supports the original call, contradicts the call, or is inconclusive.
Whenever a third umpire decision is signalled by an on-field umpire, the third umpire gets access to instant replay to make his decision. The instant replays are also available to the TV/Internet viewers. However, the live crowd does not get to witness it. Because in most of the cases, third umpire decisions end up in a tight gap between out and not out. A live crowd will make their decision on the replay shown. However, the third umpire is required to follow guidelines which may not be known by the crowd.
After the Stuart Broad incident, in The Ashes 2013, ICC has started to take steps to give third umpire access to instant replays. This is regardless of calls being referred to by on-field umpires. By doing so, ICC wants to make sure that any obvious mistakes are avoided in future.