Well if you did, how was it? Has anybody done one for a traffic ticket. I always wonder this when I am working physics problems. Thanks for the stories 
This is strictly anecdotal, but my father (a physics professor) claimed to have a co-worker who successfuly defended himself on a speeding charge by claiming that a radar gun would not provide an accurate reading on a metal-truss bridge due to reflection from the girders.
in addition, it is fairly common to determine the speed of a vehicle prior to a collision by measuring the length of the skid marks. This is an application of simple mechanics.
I did. Well I wasn’t in court but my sheet of calculations got a speeding ticket dismissed.
A friend on his motorcycle was given a speeding ticket, the speed being obtained from a laser gun being aimed by hand at traffic crossing the Golden Gate Bridge at rush hour (extremely busy).
Laser guns are supposed to be mounted, not hand-held (at least at that time) which was one point against the CHP.
I did a quick bit of geometry to show that if the clocking officer’s hand had wavered by a very small amount (it was a fraction of an inch) then the laser dot at the distance my friend was tagged from (well over 100 feet) could have been off by many feet (enough to be pointed at a vehicle in another lane).
The ticket was dismissed. The officer took the piece of paper with my sketch on it, looked at it, folded it up and stuck it in his pocket. I assume that he uses his laser gun from a fixed mount these days…
There are plenty of cases that hinge on matters of engineering, those are probably won and lost all the time on the basis of math/science (either good or bad). I had professors in college who were expert witnesses and used to provide us with real-life examples of the result of bad design and math mistakes.
The Kansas City Hyatt skywalk collapse is one example that leaps to mind.
I once got a traffic ticket dismissed by, I think, threatening to bore the judge to death. I came in with drawings, handouts, an easel ( I use all these things for providing expert witness testimony for my job). I think he was afraid he was going to miss lunch, so he just dismissed the case at the start.
Hey, not the strategy I had planned, but since it all worked out, I’m not complaining, and may even use it again someday!
This is second-hand anecdotal evidence, but a friend of mine once said that he presented measurements and math in court that disproved the cop’s claims in a traffic stop. (I forget the details now, but I think it had to do with a speed measurement by pacing.)
The judge granted that the math was probably right, but ruled him guilty anyway. Legal judgments don’t necessarily bear any relation to the truth.
I’m so glad you asked this question, because I get to tell you two of my favourite anecdotes.
First story:
Recently I was involved in a massive trial, acting for one of the defendants. The plaintiff provided a report from an “expert” about a year ago that hinged very significantly around calculation of momentum. The “expert” calculated momentum using the formul m=mv[sup]2[/sup] :eek: I remembered my high school physics. The whisper went out through the defendant’s legal teams. We purchased high school textbooks. We lay in wait and hoped, although we fully expected that at some time during the 12 months between delivery of the report and the trial someone on the plaintiff’s legal team would wise up and he’d amend his report. It never happened. The “expert” gets in the witness box and cross examination arrives:
“Mr So-and-so, what is the formula for momentum?”
“mv[sup]2[/sup]”
“Mr So-and-so, would you mind looking at this High School Physics Primer, particulary on page 45?”
Ahh, a fun moment. It took two textbooks before he backed down. There aren’t a lot of rocks in a witness box under which to hide, but if there’d been any, that’s where Mr "Expert"s head would have been.
Next story:
When I was a very junior lawyer I was assisting on the prosecution of someone who had fitted a shunt in parallel around their electricity meter. The accused brought along an “expert” electrician who, while keeping a straight face, gave evidence that this may actually have significantly increased the electricity billed to the accused because the additional wire would have decreased the resistance through the accused’s household wiring 
The judge dismissed the charge, mentioning in particular that the wire around the accussed’s meter may have “increased his bills”.
Back then I was very junior and it wasn’t my case. But bearing in mind the duties of an expert to assist the court and tell the truth, if that happened to me tomorrow, I’d be making a complaint to that witness’ professional body suggesting he be reprimanded or struck off for either lying or incompetence, one or the other.
So to answer your question, yes maths and physics are used to win and lose cases
Here’s one from the other side… I once knew someone who worked as a sonographer, and he was called in to serve on a jury for a speeding ticket. And the defendant’s lawyer tried to argue that the presence of large moving objects near the defendant’s car, such as a passing truck, could throw off the radar gun’s reading (!)
Needless to say, this guy works with waves all day and knew it was a complete fabrication. He explained it to the jury and they voted to convict. Score 1 for fighting ignorance!
Hijack: I’m curious as to something: what does the Hyatt’s lobby look like today? Can I assume they never rebuilt the walkways? I assume so, because, I mean, who’d want to go on them after that?
Out of curiousity, what was the original defense going to be?
My story is about a prof at the local university. Apparently the police had witnesses that a car’s wheels had left the ground going over a hump-backed bridge, and he calculated that for that to happen it must have been breaking the speed limit.
Actually, it can work that way; if there is a vehicle moving in the opposite direction from the one being measured, it is possible for the beam to reflect off the target, to the other vehicle, back to the target and back to the measuring device; in this (rather unlikely, but not entirely impossible) case, the speed measured will be the sum of the two vehicles (the speed at which they are moving apart), which could be up to twice the posted limit without either vehicle breaking the law.
My father, a surveyor, got off a ticket for going through a red light by asking the cop involved a series of questions. The police car had been coming the other way and my father had turned in front of him. He asked “How fast do you estimate I was travelling?”, “How far from the stop strip was I when the lights changed?”, “How long between amber and red at those lights.”, “How far does it take an average vehicle to stop at the speed I was travelling.” etc and proved that by the cop’s own evidence he would have been unable to stop except in the middle of the intersection. He was baffled why he was booked at all because he insisted the light wasn’t even amber. “Who would turn in front of a police car through a red light?” he asked.
Mind you, years before he had been pulled over on the highway for speeding with my mother asleep in the passenger seat and us kids in the back. He told the cop he was rushing home because his “wife was ill”. The cop offered an escort to the hospital and dad had to backpedal with assurances that she “wasn’t that sick”. We kids were awe struck by his brazen lying.
My brother had a physics prof in college who defended himself on running a yellow light. He had calculated that it was physically impossible to stop a vehicle (going the speed limit ) in time due to the geometry of the intersection. The road curves; the spot where the traffic light becomes visible is too close to the
stop line assuming a car doing the speed limit and accepting standard braking distance values.
Apparently it went over everyone’s head and the judge dismissed the case.
Well, there’s the famous case where Abraham Lincoln won a case by using an almanac to show that there was no moon on the night a witness claimed to have seen something by the light of it. It sounds like Presidential Legend, on the order of Washington’s tossing a dollar across the Potomac, but it’s apparently true. See the references in Richard Shenckman’s book. Apparently the issue is a little more complex than I’ve suggested – there was a lengthy and interesting article on this in Sky and Telescope , but I’ve forgotten the details.
John Allen Paulos, in his book Innumeracy, talks about a court case in which both sides used probability to argue for a client’s innocence or guilt. The prosecution calculated that the chances of anyone matching the description given were one in a million. The defence showed that, evenm if you accepted those numbers, in a city the size of LA, there were still plenty of people who ought to meet the criteria, on the basis of staistics alone.
The main quality of a professional mathematician is not a facility with numbers, but a steadfast dedication to rational thought and attention to detail.
As such, this is how mathematics (in this more general sense) would have acquitted such a defendant: by pointing out that it is only a crime to run a red light.
Well, sure, it’s used all the time. I’ve seen a computer model showing that a delivery van driver could not possibly have seen the small child on a bike in time to stop, even if he were driving at the speed limit or even at a paranoid, careful crawl through the neighborhood It was all about sight lines, speed, and braking time.
The plaintiff’s lawyer wanted to claim he was speeding and was careless and reckless and whatever else. Not only did the defendant claim he wasn’t speeding, but they were able to show that given braking time needed for that van, his speed was immaterial. The way that kid shot out in front of the van, it would have been physically impossible for him to stop in time. It had nothing to do with attention or speed, and everything to do with what the kid did.
Um, correct me if I’m wrong, but isn’t it illegal in most jurisdictions to enter an intersection when the light is yellow? (As long as one is able to safely stop, of course.)
I did, but not with strict calcs, just two pencils.
I got hit by a guy going through an intersection with blinking yellow lights. He was coming from my left, but was watching the cars on HIS left and ran into my left rear bumper. The impact turned my car 60 degrees to the left, I jumped the island, went head-on into oncoming traffic, managed to dodge everyone and u-turn my car 270 degrees to the right, back into the proper direction. The cops came and he said it was my fault, yadayadayada, and they gave both of us tickets.
Went to court. Met with the DA. He wasn’t happy with my previous record and started to say that he wasn’t going to give me a break on the careless driving. I said “I’m not looking for a break, I’m looking to get it completely dismissed.” And he asked why and I took two pencils and said “If I was hit in the left-rear bumper, turned sideways, jumped the curb, missed the oncoming traffic, pulled a u-turn 270 degrees…how could I have been going ‘too fast’, especially when it was raining?” He took the pencils, went through the motions and said “You’re right, you must have been doing under 30, otherwise you would have jumped the island and kept going into the building. Dismissed.” If it had gone to a judge, I would have done all the calcs and brought in drawings, etc.
-Tcat
Dunno how universal this is, but around these parts… “AMBER means ‘Stop’ at the stopline. You may go on only if the AMBER appears after you have crossed the stop line or are so close to it that to pull up might cause an accident”
Unless you’re leaving something out of this story about the defendant’s claim, this is entirely wrong. It’s well known that a larger object (e.g. a truck) moving near the radar gun’s target will naturally give a larger reflection of the radar signal, possibly producing an erroneous reading on the gun. And there are many other known sources of radar errors, including from stationary objects.
Furthermore, a sonographer works with sound waves, which behave quite differently in many respects from light waves (radar is “light” in a lower frequency), and wouldn’t necessarily be better informed in this area than anyone else.
Of course, it’s entirely possible the defense was trying to unload a total pile of bullshit and your friend expertly saw through it. But as you’ve described it here, this was not a triumph for justice, but a case of a little learning being a dangerous thing.