With the proliferation of speed cameras on the nation's roads, more and more of us are becoming accustomed to the bitter aftertaste that results from being caught in the glare of a well-placed radar trap.
We may moan and stamp our feet, but the police officer or the piece of paper from the council are backed up by the (mostly) irrefutable proof of technology's gaze. The machines have proved our speed beyond all reasonable doubt, and that's that. Live with it, sir.
Imagine then for a moment that you live in the great state of Ohio, where the Supreme Court ruled this month that a police officer's visual estimate of a car's speed is sufficient to issue the driver with a ticket. That's right - in the land of the free a policeman's best guess is good enough to convict.
And how is the training of these superhuman speed traps conducted? Well, they stand by the side of the road during a five hour course and guess the speed of cars going by, then see how it matches up to what an old-fashioned (and presumably almost redundant) radar gun says.
That's it. No elaborate timing method against a fixed object or trailing with an unmarked car, just the infinitely subjective stare of an entirely fallible human between you and a fine.
Marvellous. But surely this is one of those ridiculous Americanisms like prohibition or TV evangelism – it could never happen here. We're too sensible, too in love with facts and figures and measurements to base the rule of law on guessing games.