DRS in Cricket Explained: How the Decision Review System Works
The Decision Review System (DRS) lets a team ask the third umpire to check a decision made by the on-field umpire. It exists to correct clear mistakes, not to re-umpire every close call. This guide explains who can ask for a review, what the third umpire looks at, and why some reviews end with the original decision standing.
A short history
DRS was first trialled in a Test between India and Sri Lanka in 2008 and was adopted for Test cricket the following year. It later spread to One Day Internationals and T20 Internationals. Before DRS, the third umpire could only rule on line decisions such as run-outs and stumpings, which the on-field umpires referred upstairs themselves.
Who can ask for a review
- The batting side: only the batter who has been given out can review, after a quick word with their partner.
- The fielding side: only the captain can review a not-out decision, usually after talking to the bowler and wicketkeeper.
The review is requested with a “T” sign made with both arms, and it has to come within about 15 seconds of the ball becoming dead. A signal after the time limit, or a hint from the dressing room, is not allowed.
How many reviews a team gets
Each team has a limited number of unsuccessful reviews per innings, set by the ICC playing conditions for each format. A review that overturns the decision is kept. A review that ends in “umpire's call” is also kept, so a team only loses a review when the third umpire finds the on-field decision was right.
What the third umpire checks
The third umpire works through the evidence in order and stops as soon as the answer is clear.
- No-ball check: if the batter is out, the front foot is checked first. A no-ball means the batter cannot be out bowled, caught or LBW from that delivery.
- Did the ball hit the bat? Replays, sound-based edge detection and, at some grounds, heat-based cameras show whether bat or glove touched the ball.
- For LBW, ball-tracking: the system shows where the ball pitched, where it hit the pad and whether it would have gone on to hit the stumps.
Umpire's call, explained
Ball-tracking is a prediction, so it has a margin of error. When the projection shows the ball only just clipping the stumps, or hitting the pad right on the edge of the line of the stumps, the system cannot be sure the on-field umpire was wrong. In those cases the original decision stands. This is umpire's call.
That is why the same delivery can produce two different results. If the umpire said out, a marginal ball-tracking result keeps the batter out. If the umpire said not out, the same result keeps the batter in. The review only overturns a decision when the evidence clearly contradicts it.
The end of the soft signal
Until 2023, an on-field umpire referring a low catch also had to give a “soft signal” of out or not out, which the third umpire needed conclusive evidence to overturn. The ICC abolished the soft signal from 1 June 2023. The third umpire now decides low catches on the evidence alone.
Related reading
DRS is most often used for LBW, so read our LBW rule explained or try the Is It LBW? quiz. For every law of the game, see our cricket rules guide.