The Third Umpire and DRS: How Reviews Work in Modern Cricket
The Decision Review System (DRS) allows teams to challenge on-field umpiring decisions using ball-tracking technology and ultra-edge detection. This article explains how the review process works, what technology is used, and the strategic decisions behind when to review.
How a Review Is Initiated
A review can be requested by any on-field player (batting or fielding team) within 15 seconds of the umpire's decision: the reviewing player signals for a review by making a 'T' shape with their hands (fingers of one hand across the wrist of the other — the standard review signal); the on-field umpire acknowledges the review signal and refers the decision to the third umpire (an off-field umpire positioned in a review room with access to all available technology); the third umpire examines the available evidence and communicates their decision to the on-field umpires via earpiece; and the on-field umpire signals the revised or confirmed decision to the scorers and batsman. Each team has a limited number of unsuccessful reviews per innings (typically 2 in Tests, 1 in T20s, 2 in ODIs) — a review that fails (the original decision is upheld) costs the team one review from their allocation.
What Technology the Third Umpire Uses
The third umpire uses several technologies depending on the decision type: Hawk-Eye (ball-tracking technology) for LBW decisions — the ball's trajectory is tracked from the release point and a predictive model estimates where the ball would have gone after the impact point if the batsman's leg hadn't been in the way; Ultra-Edge or Snicko (acoustic edge detection) for catches — a microphone in the ground near the bat measures sound waves at the moment of ball-bat contact to confirm whether the ball hit the bat or pad; Hotspot (infra-red imaging) for edge confirmation — a heat trace appears on the bat or pad where contact occurred; and multiple high-frame-rate cameras (for run-outs, stumpings, and no-ball decisions — which don't use predictive models but require frame-by-frame visual review of precise moments).
The Strategic Decision: When to Review
Teams must decide strategically when to use their limited reviews: a team that uses both reviews on marginal LBW decisions early in an innings has no protection for clear wicket-taking opportunities later; the 'umpire's call' concept (when the ball-tracking shows the ball hitting the stumps by less than 50% of the ball's surface area — the on-field umpire's decision is upheld) means that reviews of borderline LBW decisions carry a risk of failure even when the tracking shows the ball hitting; and reviews for run-outs are generally worth taking (the technology can definitively confirm or deny whether the bat/foot was grounded before the stumps were broken — the technology is binary rather than predictive, so the result is near-certain). Experienced captains and batting coaches develop specific 'review criteria' — internal standards for when reviewing is worth the lost review if unsuccessful.
Frequently asked questions
What is 'umpire's call' and why does it mean the review fails?
'Umpire's call' in DRS refers to when the ball-tracking prediction shows the ball is hitting the stumps by less than 50% of the ball's diameter — the decision is marginal enough that the original umpire's call is retained rather than overturned. The reasoning: ball-tracking models have measurement uncertainty (typically ±10 millimetres) — a ball that tracking shows clipping the top of the stumps by 5mm might actually be missing by 5mm or hitting by 15mm within the model's error range. 'Umpire's call' acknowledges this uncertainty: for marginal decisions, the umpire's real-time judgement is considered as reliable as the predictive model. For the reviewing team, an 'umpire's call' result means the decision is not overturned — but crucially, they retain their review allocation (the failed review doesn't cost them a review if the result is 'umpire's call').
Can the third umpire initiate a review themselves without a team requesting one?
Yes — in specific situations, the third umpire can intervene without a team review: no-ball checks (in most professional formats, the third umpire automatically checks for no-balls on every ball where a wicket falls — the on-field umpire calls the batsman out, then waits for the third umpire's no-ball confirmation before signalling the dismissal); and front-foot no-balls in T20 internationals (in some tournaments, the third umpire monitors front-foot no-balls on every delivery, removing that responsibility from the on-field umpires entirely). However, for wicket decisions (LBW, catch, stumping, run-out), the third umpire can only review when a team requests — they cannot intervene on their own judgment that an incorrect decision was made by the on-field umpires.
Why are T20 teams given fewer reviews than Test teams?
T20 teams receive fewer reviews (typically 1 per innings vs 2 per innings in Tests) for practical reasons: T20 innings are shorter (typically 120 deliveries vs 300-500 in Tests) — there are fewer decisions to potentially review, and one review provides roughly proportional coverage; the time available between deliveries in T20 cricket is shorter (approximately 30-45 seconds between balls vs 60+ seconds in Tests) — more reviews would more frequently slow down an already fast-format game; and the tactical value of reviews is different in T20 cricket (protecting a set batsman's wicket for a longer innings is worth more in a 5-day Test than in a 20-over game where even a 'rescued' batsman has limited overs to contribute). The different review allocations reflect the different playing conditions and strategic values of wickets in each format.