Cricket DRS Explained — How the Decision Review System Works
Everything you need to know about the DRS in cricket: ball-tracking, Ultra Edge, Hot Spot, how many reviews each team gets, and what umpire's call means.
What is the DRS?
The Decision Review System (DRS) is a technology-based process used in international cricket that allows players to challenge on-field umpiring decisions. It was developed to reduce the number of clear on-field errors — particularly LBW calls and caught-behind dismissals — while keeping the on-field umpire's judgment as the first authority. DRS was trialled from 2008 and became a standard part of ICC Test cricket from 2009, with phased rollout to ODIs and T20Is.
How many reviews does each team get?
In Test cricket, each team receives two unsuccessful reviews per innings. If a review results in the on-field decision being overturned, the team retains the review. If the decision stands, the team loses that review. In ODI and T20I cricket, each team receives one review per innings. Reviews reset at the start of each innings, not each session.
What technology does DRS use?
DRS combines several technologies: Ball-tracking (brand names: Hawk-Eye, Virtual Eye) plots the ball's trajectory using multiple cameras and projects where it would have gone after pitching — essential for LBW decisions. UltraEdge (also called Snickometer or Real Time Snickometer) detects tiny spikes in audio coinciding with the ball passing the bat's edge, helping adjudicate caught-behind decisions. Hot Spot uses infrared imaging to detect heat marks left on the bat or pad when the ball makes contact — effective for catches but weather-dependent. Hawk-Eye ball-tracking has become the most commonly used and debated component, particularly for LBW decisions.
What does 'Umpire's Call' mean?
Umpire's Call is the most controversial element of DRS. For LBW decisions reviewed via ball-tracking, the system plots the projected trajectory with a margin of error. If the ball is projected to hit the stumps but only clipping the edge of the wicket — within the margin of uncertainty — the system designates this 'Umpire's Call'. This means the on-field decision (out or not out) stands, regardless of what the reviewing team hoped. Crucially, if the on-field decision is upheld via Umpire's Call, the reviewing team does not lose their review — they retain it. This prevents teams being penalised for reviewing a marginal decision where the technology itself is uncertain.
Catches and DRS
For caught-behind dismissals, the third umpire uses UltraEdge to detect whether the ball touched the bat. A visible spike on the audio trace — especially one coinciding exactly with the ball passing the bat — is strong evidence of an edge. The absence of a spike suggests the ball missed the bat. Hot Spot provides supporting evidence via heat marks. For catches at field level, the third umpire reviews camera angles to determine whether the fielder had complete control of the ball, that their feet did not touch the boundary, and the ball was cleanly taken — all three must be satisfied for a clean catch.
Frequently asked questions
Can a batsman review an LBW that was given out?
Yes. Either the batting or fielding team can initiate a review on any on-field decision. The batting team typically reviews LBW dismissals; the fielding team reviews not-out LBW appeals and not-out caught-behind appeals.
What happens if DRS technology is not available?
If DRS is not available (technical failure, or a bilateral series where both boards haven't agreed to use it), no reviews are available and all on-field decisions are final. DRS has not always been mandatory — some series have been played without it, particularly in the past.
How long does a DRS review take?
A typical DRS review takes 60–90 seconds. The third umpire checks available technology and relays the decision to the on-field umpires. Complex cases, particularly where multiple technologies need reviewing, can take 2–3 minutes.