DRS in Cricket Explained — How the Decision Review System Works
A complete guide to the Decision Review System (DRS) in cricket: what technology is used, how teams use their reviews, what 'umpire's call' means, and the history of DRS.
The Decision Review System (DRS) is a technology-based framework used in international cricket to allow teams to challenge on-field umpire decisions. Introduced in Test cricket in 2009 and gradually extended to all formats, DRS has fundamentally changed cricket officiating — reducing clear errors, introducing the concept of 'umpire's call', and giving teams genuine tactical choices over how and when to use their review allocations.
How DRS Works
When a team wants to challenge an umpire's decision, the batting batter (for an 'Out' decision) or the fielding captain (for a 'Not Out' decision) must make a T-sign gesture within 15 seconds of the umpire's ruling. The third umpire then conducts the review using available technology. The decision is either 'Upheld' (original decision stands) or 'Overturned' (original decision reversed). If the original decision is upheld, the reviewing team loses one of their review allocations.
| Format | Reviews Per Innings Per Team |
|---|---|
| Test cricket | 2 per innings |
| ODI cricket | 1 per innings |
| T20 International | 1 per innings |
Technology Used
- Hawk-Eye: ball-tracking that reconstructs the ball's flight path before and after pitching, used for LBW projection
- UltraEdge (Snickometer): matches audio spike with ball position to detect bat-ball contact for edge decisions
- Hot Spot: infrared imaging that detects heat signatures from ball-bat friction (not used in all matches)
- Ball-tracking cameras: high-speed cameras at multiple angles for run out and stumping frame-by-frame review
- Real Snicko: advanced version of the snickometer that provides real-time audio analysis
Umpire's Call
Umpire's call is the most controversial aspect of DRS. When ball-tracking shows the ball hitting the edge of the stumps within a defined uncertainty zone (approximately 2.5mm), the original umpire's decision is retained — the technology is acknowledged to be imprecise at this margin. Crucially, a review that results in umpire's call does NOT cost the reviewing team their review — they keep their allocation.
History and Controversy
DRS was introduced after years of high-profile umpiring errors in major matches. It was initially rejected by the Board of Control for Cricket in India (BCCI), meaning India-hosted Tests lacked DRS for several years. This created anomalies where some series had DRS and others didn't. Universal DRS adoption across all ICC events followed India's eventual acceptance of the system, though debates about umpire's call and the accuracy of ball-tracking continue.
Frequently asked questions
What happens when both teams use all their DRS reviews?
Once a team has exhausted their DRS reviews for an innings, they cannot challenge any further decisions in that innings. Play continues with on-field umpire decisions being final until the next innings begins, when each team's review allocation is reset.
Can a team use DRS to challenge a wide ball?
No — DRS can only be used to challenge decisions on dismissals (caught out, LBW, run out, stumping, obstructing the field). Wide balls, no-balls (except height no-balls in some competitions), and other on-field decisions cannot be reviewed using DRS.
What is the difference between DRS and the third umpire?
DRS is the system used when a team requests a review of an on-field decision. The third umpire is the official who conducts all TV-based reviews — including DRS requests and referrals made by on-field umpires for boundary calls, run outs, or unclear catches. The third umpire conducts both DRS reviews and non-DRS referrals.