South Africa were denied a crucial breakthrough on the first day of the World Test Championship final by umpire's call.
Even coming soon after lunch on the first day, it felt like a pivotal moment. South Africa had won the toss and chosen to bowl first under cloudy skies. Four first-session wickets were their reward, and they headed into the first interval of the World Test Championship final on top. One more scalp would have brought wicketkeeper Alex Carey to the crease with fewer than 100 on the board. After him the bowlers.
Final, South Africa vs Australia
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Marco Jansen thudded into Beau Webster’s front pad, the all-rounder propped forward in defence but failing to get bat on ball. Both men are tall, but the decision to go upstairs looked a good one. Bounce wasn’t an issue, and nor was line, the ball projected to be thudded into middle stump. And yet Webster was reprieved, the technology revealing that the centre of the ball had been outside of the line of the stumps when it hit Webster’s front pad, not quite enough to overturn the on-field decision. Had he been given out, it would have stayed out. But he wasn’t.
Read more: This has been the year of the streak-ender, is this finally South Africa's time?
Is umpire's call in place to account for technology's margin of error?
For some, this was puzzling. Often it’s said that umpire’s call is in place due to the margin of error in the technology, with projected paths uncertain and so some leeway either way needed. But where the ball hits the batter is a matter of fact, rather than needing any guesswork. So why are any caveats needed?
In fact, this gets at a common misconception about how accurate ball-tracking technology is, and about the purpose of umpire’s call in the first place. The ‘umpire’s call’ zone extends half a ball’s width from the stumps, or about 35mm. In 2015, Paul Hawkins, the inventor of HawkEye, put the maximum margin of error for the technology at between 5 and 10mm, well below this distance, and that margin has since reduced considerably.
“We are a lot, lot more accurate than the size of the umpire’s call area,” Hawkins said last year. “If you start from scratch, is there a reason for the umpire’s call? Probably not. Most other sports, it would be a definitive, ‘it’s out or not out’.”
A couple of scenarios also help explain that margin of error is not the main consideration. Were that the only factor, we could be more sure of an lbw projection that hits the batter very close to the stumps, and so could have a smaller umpire’s call zone. Instead, the umpire’s call zone remains the same wherever a batter is hit. Also, if you consider a ball that is projected to be missing the stumps by a whisker, this isn’t considered to be in the umpire’s call zone. If there were a significant margin of error, it’s plausible that a ball that is just missing might actually have been hitting.
So why does umpire's call exist at all?
The clue is in the name: it’s to leave some power with the on-field umpire. DRS is there to eradicate the howler, not to re-umpire the game. Cricket, through its history, has generally accepted that if a ball is just clipping the stumps, ‘not out’ is a fair enough decision.
Removing umpire’s call, and saying that every ball projected to be hitting the stumps should be lbw, as long as the other conditions are met, would be a significant change to the game as we know it. It would, on the face of it, give bowlers a significant advantage - every current not out umpire’s call decision would be given out, and there would be no extra not out decisions in the other direction.
Whether a batter is hit in line or not is an extension of this. It’s not about the technology, it’s about sticking with the umpire’s decision unless it’s significantly incorrect. Webster was fortunate. And even more so an over later when South Africa declined to review an lbw decision that would have been overturned.
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