DRS in Cricket Explained: How the Decision Review System Works
Understand the Decision Review System (DRS) in cricket — what technologies it uses, how teams review decisions, Umpire's Call, and the controversy around DRS.
The Decision Review System transformed cricket from a game entirely dependent on on-field umpiring to one where technology provides a second layer of accountability. DRS is now standard in all major international matches — and understanding it is essential to following modern cricket.
What Is DRS?
DRS is the ICC's framework for using technology to review on-field umpiring decisions. It includes several separate technologies — ball-tracking, edge detection, snickometer — all reviewed by the Third Umpire (a match official situated off the field with access to multiple camera feeds and data systems).
DRS Technologies
| Technology | What It Does | Used For |
|---|---|---|
| Hawk-Eye / ball tracking | Tracks the ball's 3D trajectory and projects its path | LBW decisions — would the ball have hit the stumps? |
| UltraEdge / Snickometer | Detects edges from the bat using audio waveform spikes synced with video | Caught behind decisions — did the ball touch the bat? |
| HotSpot / infra-red imaging | Thermal camera shows heat generated by contact with bat or pad | Edged catches — confirms contact point |
| Ball Spin Tracking | Measures revolutions and axis of spin | Supplementary for spinners in LBW reviews |
How DRS Reviews Work
- An on-field decision is made by the umpire (Out or Not Out)
- The captain of the aggrieved team signals a review — typically a 'T' shape with both hands within 15 seconds of the decision
- The Third Umpire reviews the relevant technology in sequence
- The Third Umpire communicates their findings through the stadium system (replays are shown on the big screen)
- The on-field umpire either upholds the original decision or overturns it
- If the review succeeds (decision overturned), the team retains their DRS review. If it fails, the review is used up
DRS Allocation: How Many Reviews Per Team?
Each team is allocated 2 DRS reviews per innings in Test cricket and 1 review per innings in ODIs and T20Is. Reviews are retained if the original decision is overturned ('Review Successful'). Reviews are lost if the Third Umpire upholds the original decision ('Review Unsuccessful'). A review is also retained if 'Umpire's Call' applies to the result.
What Is Umpire's Call?
Umpire's Call acknowledges the inherent margin of error in ball-tracking. If ball-tracking shows the ball 'clipping' the stumps — hitting less than half the ball against the stumps — the on-field decision is retained. The reviewing team does not lose their DRS review if the result is Umpire's Call.
DRS Controversies
- Ball-tracking's predictive accuracy over long distances has been questioned — the further the ball has to travel after impact, the less accurate the projection
- HotSpot has missed edges that Snicko detected, raising questions about which technology is definitive
- BCCI resisted adopting DRS for several years, arguing the technology was not reliable enough — India finally adopted it in 2016
- Umpire's Call frustrates players and fans when a ball-tracking graphic shows near-certain stump contact but the on-field decision stands
- Different DRS providers are used in different countries, creating technology inconsistency
Frequently asked questions
Who can trigger a DRS review in cricket?
Only the captain of the relevant team can officially request a DRS review. In practice, the batsman about to leave the crease can signal to their captain, and the fielding team's bowler or wicketkeeper can signal to their captain — but only the captain can make the formal 'T' sign to trigger the review.
What happens if a team has no DRS reviews remaining?
Once a team has used their DRS reviews, they cannot challenge further on-field decisions for the remainder of that innings. They receive a fresh allocation for the next innings. This creates tactical situations where teams must conserve reviews for crucial moments.
Is DRS available in all cricket matches?
No. DRS requires expensive technology infrastructure. It is available in all ICC-sanctioned international matches (Tests, ODIs, T20Is), but may not be available in domestic matches or matches in countries without the required broadcast setup. The host broadcaster typically provides the DRS technology.
What does the 'soft signal' mean in DRS?
The soft signal is the on-field umpire's initial decision communicated before a TV review is triggered. For low catches (where the fielder might have grassed the ball), the umpire gives an initial soft signal of Out or Not Out. The Third Umpire must find conclusive evidence to overturn the soft signal — if inconclusive, the soft signal stands.