The third umpire is an off-field umpire who officiates decisions referred to by the two on-field umpires in an international cricket match. The third umpire has the aid of television camera replays to come to a decision. An on field umpire can use his discretion to refer a close decision to the third umpire to refer to dismissals, catches or boundaries via a wireless set.

In the case of a run out or stumping, a batsman may be declared "out" if the wicket is 'put down'. The wicket is down if a bail is removed from the top of the stumps or a wicket is struck out of the ground, whether by the ball, the bat or the striker's person. If the batsman is caught between the two popping creases if the wicket is put down, the batsman is declared out. In most cases, the event occurs in a fraction of a second. Unable to accurately come to a decision on the dismissal of a batsman, the umpire requests the third umpire to ascertain whether the batsman had made it home. The third umpire then looks at various TV replays from different angles and comes to a conclusion by pressing the appropriate signal. A red light indicates that the batsman is out and a green one otherwise. 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.

A batsman is out caught 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 was 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, 4 runs are declared. A third umpire may also be consulted in such a case.