DRS and Third Umpire: How Technology Changed Cricket's Decision Making
How the Decision Review System works in cricket — the technology used (ball-tracking for LBW, UltraEdge/Snickometer for edges, HotSpot for impact, Hawk-Eye for trajectory), how teams use their review allowances, why DRS was introduced to reduce wrong decisions, the ongoing debates about DRS accuracy, and how the third umpire's role has evolved in the technology era.
The Technology Stack
The DRS (Decision Review System) uses multiple technologies simultaneously. Ball-tracking: Hawk-Eye (or equivalent) traces the ball's trajectory from the moment it leaves the bowler's hand, predicts where it would have hit the stumps for LBW decisions, and provides 3D visualisation of the delivery. Edge detection: UltraEdge (also known as Snickometer) uses a microphone system near the batsman's crease to detect the sound spike that indicates the ball has hit the bat edge — paired with video to confirm the timing of the sound spike relative to the ball's contact with bat or pad. HotSpot: an infrared camera system that detects temperature differentials on the bat's surface — a ball contacting the bat generates friction heat that shows as a spot on infrared. Stump cameras and Hot Spot are complementary systems used together.
How Reviews Work
Each team is allocated a specified number of unsuccessful reviews per innings (typically 2 in Tests, 1 in limited-overs cricket). A review can be requested by the batting team (to overturn a dismissal they believe was not out) or the fielding team (to overturn a not-out decision they believe was incorrect). After a review request, the third umpire examines the available technology evidence and communicates the finding to the on-field umpires via earpiece. If the decision is changed ('out' becomes 'not out' or vice versa), the team that requested the review retains their review. If the original decision stands, the review is lost. If the third umpire finds the technology 'inconclusive' (insufficient evidence to overturn), the original decision stands and the review is retained.
Impact on Umpiring
DRS has measurably reduced wrong decisions in international cricket — analysis of pre-DRS vs post-DRS error rates shows a significant reduction in obviously incorrect LBW and caught-behind decisions. However, DRS has also introduced new debates: the Hawk-Eye 'ball-tracking' for LBW involves a significant degree of computer modelling (the ball changes direction after pitching, and predicting where it would have gone without the batsman's body is inherently probabilistic). The 2.5m rule (if the batsman was hit more than 2.5 metres from the stumps, the full-pitch uncertainty in the Hawk-Eye model means 'umpire's call' applies even if the model predicts hitting) is particularly controversial — some dismissals stand or are overturned based on a judgement about the model's uncertainty range rather than a clear fact.
Frequently asked questions
Is DRS available at all international cricket matches?
DRS availability varies by match and host board. ICC full-member bilateral series between top nations almost always have DRS. Some lower-ranked bilateral series, particularly involving Associate members, may not have full DRS due to the technology cost (the complete ball-tracking and edge-detection setup costs significant money to deploy and operate). The ICC has been expanding DRS availability — it is now standard at ICC-hosted tournaments (World Cup, World Test Championship fixtures, Champions Trophy). Domestic T20 franchise leagues (IPL, PSL, BBL) also use DRS with their own systems. The specific technology brands differ between venues — some use ball-tracking systems from companies other than Hawk-Eye — but the principles are consistent.
Can teams use DRS for no-ball decisions?
No — teams cannot request a DRS review for no-ball decisions. No-balls are the sole responsibility of the on-field umpires (front-foot no-balls are monitored by the square leg umpire). However, the third umpire monitors no-balls in some competitions through a dedicated system — not under team-request DRS but as part of the official monitoring framework. In some formats, the third umpire checks every delivery for no-balls (the technology reviews automatically rather than on player request). When the third umpire spots a no-ball through this monitoring, they alert the on-field umpires to call it retroactively if it was not already signalled.
How long does a DRS review typically take?
A standard DRS review in international cricket takes approximately 60-90 seconds from the moment the team requests it to the on-field umpire receiving the third umpire's recommendation. Complex reviews (involving multiple technologies — edge detection AND ball-tracking for an LBW where there may also be a bat edge) take slightly longer. The third umpire communicates verbally to the on-field umpire throughout the review, and the decision is displayed on the ground's big screen simultaneously. In broadcast coverage, the review process is one of the most watched segments — viewers see the technology readouts in real time, building tension as each element of the review is examined. Reviews that take over 2 minutes are considered unusually long and typically involve genuine ambiguity.