DRS in Cricket Explained — Decision Review System
A complete guide to the Decision Review System (DRS) in cricket — how it works, what technology is used, when teams can review, and famous DRS moments.
The Decision Review System (DRS) is a technology-based process that allows teams to challenge on-field umpiring decisions in international cricket. Introduced by the ICC in 2008, DRS uses multiple technologies to provide a more accurate decision on dismissals — particularly LBW, catches, and stumpings — reducing errors in high-stakes matches.
How DRS Works
Each team gets 2 DRS reviews per innings (3 in Test matches per innings). After the on-field umpire gives a decision, the batting or fielding side can challenge it within 15 seconds by making the TV screen rectangle gesture. The third umpire in the control room then reviews the available technology to reach a decision. If the review is upheld (the decision changes), the team retains that review. If it fails, the team loses one review.
Technologies Used
- Ball-tracking (Hawk-Eye): uses six high-frame-rate cameras to map the ball's trajectory in 3D. Predicts where the ball would have gone had it not hit the batter's pad — used for LBW reviews.
- Hotspot: an infrared imaging system that detects friction-heat from ball contact. Shows whether the ball hit the bat edge or pad — used for caught-behind and bat-pad appeals.
- UltraEdge (Snickometer): detects acoustic spikes in the stump microphone feed at the same time the ball passes the edge — used to confirm or deny an edge on caught-behind reviews.
- Real-time stump microphones: audio evidence of ball-on-bat or ball-on-pad contact.
LBW DRS Review Process
LBW reviews use ball-tracking most prominently. The third umpire checks: (1) was there a bat edge first? (2) did the ball pitch outside leg stump? (3) where did the ball hit the pad? (4) where would the ball have hit the stumps? Hawk-Eye's prediction uses a 2.5 metre rule — if the impact was within 2.5 metres of the stumps, ball-tracking is considered accurate enough to override the on-field call. Beyond 2.5 metres, the on-field decision stands.
Umpire's Call
When ball-tracking shows the ball hitting the edge of the stumps — partly in, partly out — the on-field umpire's decision is upheld and labelled 'Umpire's Call'. Crucially, a review that results in Umpire's Call does not cost the reviewing team their review — the challenge is considered partially successful. Umpire's Call is one of the most debated aspects of DRS.
Frequently asked questions
How many DRS reviews does each team get?
In Test cricket, each team gets 3 DRS reviews per innings. In ODIs and T20Is, each team gets 2 reviews per innings. A review is retained if the on-field decision is overturned; if the review fails (on-field decision stands), one review is lost.
What is Umpire's Call in DRS?
Umpire's Call occurs when ball-tracking shows the ball clipping the edge of the stump — partly hitting and partly missing. In this case, the on-field umpire's original decision is upheld, but importantly, the reviewing team does not lose their review. It acknowledges that the margin of error is within the technology's accuracy limits.
What is Hawk-Eye in cricket?
Hawk-Eye is the ball-tracking technology used in DRS to predict a ball's trajectory after it hits the batter's pad. It uses multiple high-frame-rate cameras to build a 3D model of the ball's path, then extrapolates where the ball would have gone to determine if it was hitting the stumps.
Can a fielder ask for a DRS review?
Yes — either the batting or the fielding team can request a DRS review. The fielding captain initiates a review for a not-out decision they want challenged; the batting side's dismissed batter (or their batting partner) initiates a review for an out decision they want challenged. The review must be made within 15 seconds of the umpire's signal.