# Man Beat Traffic Ticket ... with Math!

I didn't do it, officer, and I can prove it ... with math!

UC San Diego physicist Dmitri Kriokov fought his \$400 traffic ticket (for runing a stop sign) and won, with this physics paper titled "The Proof of Innocence [pdf]," which he posted to arXiv:

After thinking Krioukov ran through a stop sign, a nearby police officer pulled him over and issued him a citation. According to Krioukov's paper, however, three physical phenomena combined at just the right time and misled the officer.

When Krioukov drove toward the stop sign the police officer was approximating Krioukov's angular velocity instead of his linear velocity. This happens when we try to estimate the speed of a passing object, and the effect is more pronounced for faster objects.

Trains, for instance, appear to be moving very slowly when they are far away, but they speed past when they finally reach us. Despite these two different observations at different distances, the train maintains a roughly constant velocity throughout its trip.

In Krioukov's case, the police cruiser was situated about 100 feet away from a perpendicular intersection with a stop sign. Consequently, a car approaching the intersection with constant linear velocity will rapidly increase in angular velocity from the police officer's perspective.

Physics - Is there anything it can't do? Link

I was once accused of exceeding the speed limit because an officer, who had *been parked* when I passed him, had to exceed the speed limit in order to catch up with me. I didn't get a ticket.
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I was preparing to contest a ticket for speeding based on a laser range-finder measurement. The laser ranging uses the timing of pulses to measure speed - but the pulses returned by a slightly closer car in the next lane can make the device calculate a higher speed. Any nearby car can make the device register 10-15 mph too high.

But the officer did not show up for the court date, so the judge dismissed the case without me presenting my argument.
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I did something quite similar during the time I was taking Physics back in high school. I fought the ticket by pointing out discrepancies with speed, curb weight of the vehicle, coefficients of friction, angles, the works; I even pulled up an aerial photograph of the intersection for fully accurate radius measurements and arcs (before Google Earth, this was in the Terraserver days) and visited the intersection at 3:00am when there was no traffic with strings, stakes, levels, and tape measure to meassure the angle of the bank. In the end I proved that from where the officer was (in his own words) there was no way I could have passed him at the speed he "clocked" me, and still have slowed down enough to make the curve of the exit going onto the road where he pulled me over without having locked up the tires and ending up in the grass, or if the tired HAD held (I worked all the angles), I still would have flipped the vehicle I was driving. It had to have been one of the vehicles in the other lane that were continuing down that road...
It was one of the most joyous experiences of my life, right up until the point I went to court and still had to pay the ticket. That was the day my faith in the justice system was obliterated. I still have all the drawings, equations, vehicle research, and picture (the entire file I took into court, 20 some-odd pages). I can't bring myself to throw all that work away, even after this long. Maybe I'll bring it out and show it to the kids when they get to that age. "See, THIS is when you are 'going to need this'... so get to the studies (and hope you find an honorable court room)"
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Here's a story from Norway's largest daily, Aftenposten about a geophycist whoi finally won over the police. His 25 year of working with lasers, radars and measurements must surely have helped. Google translate English here: http://translate.google.com/translate?sl=no&tl=en&js=n&prev=_t&hl=no&ie=UTF-8&layout=2&eotf=1&u=http%3A%2F%2Fwww.aftenposten.no%2Fnyheter%2Firiks%2FFrifunnet-etter-grove-feil-hos-politi-og-domstoler-6799041.html Norwegian original here http://www.aftenposten.no/nyheter/iriks/Frifunnet-etter-grove-feil-hos-politi-og-domstoler-6799041.html
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