DRS in Cricket Explained: Reviews, Ball-Tracking and Umpire’s Call

By Alventra Sports · Updated

The Decision Review System lets players challenge an on-field umpire’s decision using TV replays and technology. Here is how DRS works, what the technology checks and why some reviews end with “umpire’s call”.

What is DRS?

DRS (Decision Review System) is the process by which a team can ask the TV umpire, also called the third umpire, to check an on-field decision. It was trialled in Test cricket in 2008 and introduced officially by the ICC in 2009. Today it is used in Tests, ODIs and T20Is, and in many T20 leagues.

The aim is to remove clear mistakes, not to re-umpire every close call. That is why the on-field decision stands unless the evidence clearly shows it was wrong.

How a review works

  • The fielding captain or the batter who was given out makes a “T” sign with their arms.
  • The request must be made within 15 seconds of the ball becoming dead. A timer is shown on the big screen at most grounds.
  • The third umpire checks the replays and the technology, then tells the on-field umpire to stay with or change the decision.
  • If the review shows the decision was wrong, the team keeps its review. If the decision stands, the team loses one.

How many reviews does each team get?

Each team gets a limited number of unsuccessful reviews per innings, set by the ICC playing conditions for each format. In recent years that has been three per innings in Tests and two per innings in ODIs and T20Is, but tournaments can set their own numbers. Reviews are not topped up during an innings, and a review that ends with “umpire’s call” is not lost.

The technology behind DRS

  • Ball-tracking: cameras track the ball’s path and project where it would have gone after hitting the pad. This is used for LBW decisions.
  • Edge detection: UltraEdge (also called Snicko) uses stump microphones to show a spike when the ball touches the bat. Some series also use Hot Spot, an infrared camera that shows a bright mark where the ball hit.
  • Replays: slow-motion and high-frame-rate replays from many angles, used for catches, run-outs and stumpings.

What does “umpire’s call” mean?

For an LBW, ball-tracking checks three things: where the ball pitched, where it hit the batter and whether it would have hit the stumps. When the replay shows the ball only just clipping the stumps, or the impact is right on the edge of the line, the evidence is too close to overturn the umpire. The decision on the field stands, and the reviewing team keeps its review.

This is why the same delivery can be out or not out depending on what the on-field umpire first decided: DRS is built to correct clear errors, not to replace the umpire’s judgement on marginal ones.

Follow reviews live

Reviews and their outcomes show up in the ball-by-ball commentary on every match page. New to other terms? The cricket glossary explains LBW, run rate, follow-on and more.

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