Complete explanation of DRS in cricket — how the Decision Review System works, ball-tracking technology, when to review, and famous DRS moments.
DRS stands for Decision Review System — the technology-assisted process that allows teams to challenge an on-field umpire's decision in cricket. Introduced at Test level in 2008 and now used across all major international formats, DRS has transformed cricket officiating and reduced controversial decisions significantly.
Hawk-Eye uses multiple high-speed cameras to track the ball's path and predict where it would have gone after hitting the batter's pad. Used to adjudicate LBW (Leg Before Wicket) decisions — if the ball is hitting the stumps, the decision stands; if it's missing, it's overturned.
UltraEdge detects tiny sound spikes in the audio recorded from microphones near the bat as the ball passes. Used to determine whether the ball touched the bat's edge before being caught or hitting the pad. A spike in the audio at the moment of contact indicates a nick.
An infra-red imaging system that shows heat generated by friction when the ball contacts bat or pad. A white mark appears at the contact point. Hot Spot is not always available and is considered supplementary to UltraEdge.
The most debated aspect of DRS is "Umpire's Call" — when ball-tracking shows the ball only clipping the stumps within a margin of uncertainty, the on-field umpire's original decision stands. This means a not-out LBW can survive review even when Hawk-Eye shows the ball hitting the stumps, if the impact is within the uncertainty zone. Many feel this undermines the technology's purpose.
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