If Tony Hill gives a batsman out on an empty field, and no one is there to see it, is it out?
The answer on day three of the fourth Test at Chester-le-Street, was technically, yes - but DRS deserved the credit.
Players voted with their feet after the latest blunder from an out of form umpire.
Ryan Harris knew he was plumb lbw to Stuart Broad for the last wicket of Australia's first innings.
And the not out decision from Hill was so obviously wrong that no one even bothered to hang around in the middle for DRS to come back with its "OUT'' verdict.
In comical scenes, the New Zealander remained resolute at the stumps and raised his finger to a vacant pitch.
Harris was halfway up the race.
Perhaps Hill was visualising imaginary fielders celebrating, and a pretend batsman tucking his bat under his arm, as a reminder of what happens when a correct decision is made in the first place.
After all, practice makes perfect.
Thankfully for Hill, DRS has got him out of jail on most occasions.
By staying in the middle, Hill was following due process to the same farcical extent that's seen him twice decide, along with his fellow umpire, to send players from the field for bad light, when common sense says the game should go on.
A bemused Harris said he couldn't have tried harder to be given out for a ball that was "breaking middle''.
"I tried to walk but he still didn't give me out,'' joked the fast bowler.
"There were two noises and he obviously thought I had hit it but it hit both pads. It has happened before so I knew the feeling.
"The English guys asked me if it had hit it and I said, `no I didn't and I can't believe he didn't give me out.'''
Umpiring isn't easy, and Hill's record is good enough for him to be on the ICC's elite panel.
However, it's difficult to see how the man who gave Usman Khawaja out swinging at thin air can stand in the return Ashes series given his unfortunate run of outs.
And more to the point, his penchant for mixing them up with not outs.