DRS Complete Guide: How the Review System Works in Cricket
Everything you need to know about the Decision Review System (DRS) — technology used, how teams use reviews, and common DRS outcomes explained.
The Decision Review System (DRS) transformed cricket officiating by giving teams the power to challenge on-field umpire decisions using technology. Since its full ICC adoption in 2009, DRS has reduced howlers, sparked fierce debates, and added a dramatic new layer to big moments in Test and limited-overs cricket.
What Is DRS?
DRS is a set of tools and protocols that allow teams to request a review of an on-field umpire's decision. The third umpire in the stands examines available technology and either upholds or overturns the original call. Each team has a limited number of reviews per innings.
Technologies Used in DRS
- Hawk-Eye (Ball Tracking): predicts the ball's path after pitching to assess LBW
- UltraEdge / Snickometer: detects faint edges via audio waveform synchronized to video
- Hot Spot: infrared imaging that shows friction marks — indicates where ball hit bat or pad
- Ball Spin: shows the spin axis of the delivery
- Stump microphones: used to detect sounds at the moment of impact
Review Allowances
| Format | Reviews Per Innings Per Team | Reviews Reset? |
|---|---|---|
| Test | 2 | Yes — after 80 overs or innings end |
| ODI | 2 | No |
| T20I | 1 | No |
A team retains a review if the decision is changed (successful review). If the call stands (unsuccessful), the review is lost. This creates strategic tension — especially late in innings when reviews are precious.
Decisions That Can Be Reviewed
- Caught behind (bat-pad edge)
- LBW appeals
- Caught (including whether a catch was clean)
- Stumped
- Run out
- Hit wicket
The 'Umpire's Call' Rule
For LBW reviews, if Hawk-Eye shows the ball was only clipping the edge of the stumps (less than 50% of the ball hitting the stumps), the outcome is 'Umpire's Call.' The original on-field decision stands — and crucially, the reviewing team does not lose their review. This rule is controversial but designed to acknowledge the limits of ball-tracking prediction accuracy.
Umpire's Call in Action
Bowler appeals for LBW. Umpire gives not out. Fielding team reviews. Ball-tracking shows ball would have hit middle stump but 40% of ball misses — 'Umpire's Call.' Original not-out decision stands. Fielding team retains their review because it was marginal.
Height and Pitching Conditions
For an LBW to be upheld via DRS: the ball must pitch in line or outside off stump (not outside leg), impact must be in line with the stumps, and the ball must be going on to hit the stumps. If the ball pitches outside leg, LBW cannot be given regardless of DRS.
Controversies and Limitations
- Ball-tracking cannot perfectly predict a ball that may turn, seam, or deviate further
- Hot Spot occasionally misses very faint edges
- Different broadcasters use different tracking systems — inconsistencies emerge
- Some bilateral series do not use full DRS due to cost or broadcaster agreements
- Teams sometimes use reviews strategically even when confident the decision will stand (to waste time or unsettle opponents)
Frequently asked questions
Can you review a wide or no-ball decision with DRS?
No. Wide and no-ball decisions cannot be reviewed with DRS. They remain entirely at the on-field umpires' discretion.
What happens if both teams run out of reviews?
Play continues with only on-field umpire decisions. In Tests, reviews reset after 80 overs, so both teams get two fresh reviews at that point.
Does DRS apply in all international cricket?
DRS is mandatory in ICC-organised events and most bilateral Tests and ODIs. Some bilateral T20I series opt out. IPL uses a modified 'Impact Review' system, not full DRS.
What is the 'Ashes DRS' controversy?
Australia historically objected to DRS in Ashes series due to doubts about Hawk-Eye accuracy. From 2013 onwards both nations agreed to use it. The debate shaped how 'Umpire's Call' was refined.