First post to the forums. I used some information from the forum (especially STH and Maestro's posts) to help fight (unsuccessfully, mind you) a recent speeding ticket in Pennsylvania. I thought I would give back to the community/others by posting my research/findings - maybe it can provide some use to someone else in the future...
Background: 1/2 mile from my house I was clocked (Robic stopwatch) doing 49.1 MPH in a 35 zone (3.37 sec over 0.046 miles). The officer wrote the ticket for 40 in a 35 and noted the distance, time, and speed which all were listed or calculated to be 49.1 MPH. I drive a louder, flashy, yellow car that attracts bad attention and know I was not driving 49.1 MPH as indicated. I was timed between a fence post and mailbox that both sit about 5 feet off the far side (as viewed from the officer's location) of the road.
The trial: the cop asked the judge to change the ticket to 49.1 (twice). Judge denied the request (twice). I presented what I thought was a good case (see below), albeit technical and somewhat scattered. Judge said I did a great job on my homework but still found me guilty of 5 over.
Learned at the trial: Identified the marks the officer used to start and stop the watch (fence post and mailbox); in his testimony, he said he started before I reached the first mark and stopped after I passed the second mark - not "crossing the lines", so to speak. The officer thought the distance was 247 feet and not the 242.88 as calculated from the 0.046 miles; I have since learned that Google Earth calculates the distance as 235 feet between his two marks. He last calculated the distance 6 years ago and is SURE that nothing has changed since then (new fence, moved mailbox). He was sitting roughly 100 feet back from the road I was traveling on. I learned the officer has never had his reaction time tested or passed a "short course" as described later.
Conclusion: debating whether or not to refine my case and take it to the appeals court. 5 MPH over in PA carries no points, although the fine was $120. I think the appeal filing is $35. I can't get over how much room for error there is in the method used to calculate my speed. In hindsight, I would have put my argument better into layman's terms and created most of my argument during the cross examination vs. the defense presentation (getting him to make my point always looks better than trying to prove it myself). I'm welcome to everyone's comments/critiques of the information I am presenting and recommendations going forward...
- Parallax - Oxford English dictionary identifies parallax as "apparent difference of orientation of an object viewed along two different lines of sight"; presented example of speedometer in car when viewed head on vs. viewed from the front, passenger seat which gives two different readings; without a line painted on the road, the only way the officer could have precisely known when I crossed the marked point is by my vehicle obscuring the mark or having the mark reappear from behind my vehicle. Additionally, the roadway would not have been visible at the second mark due to a small ridge running in the grass on the near side of the road.
- Geometry - In the Driver's Guide to Police Radar, Craig (author) wrote... TDC (time distance computer) manufacturers and the National Transportation Safety Administration (NHTS) guidelines all say that a 200-foot distance between marks is sufficient, provided the officer is parked at an angle, that he's at least 300 feet from the road being monitored and the speed limit is 40mph or lower. But they also caution that only officers who've been specially trained in "short course" operation should use a 200-foot distance. Everyone else is too likely to screw up... With that said, the reason for the recommendations is that the geometry allows for too much slop. Sitting 100 feet back from the road the officers line of site to the two marks is too great of an angle from perpendicular. Further, the distance between the marks on the far side of the road is 243 feet, but the distance on the near side of the road based on his viewing angle (using tangents, et al) is more like 200 feet. Due to parallax, the only way for him to precisely know when I have crossed the line (hopefully established earlier) is when I obstruct the view of the mark or the mark reappears from behind my vehicle, then he has actually just calculated my speed over 200 to 214 feet (length of vehicle is 14 feet) and not the proposed 243. Basically, there is 29 to 43 feet of guessing when I have passed the line based on his line of sight.
- Officer Training - no doubt that I was barking up the wrong tree, but I asked the officer if he had ever had his reaction time tested and if he had ever received training to use a Robic device on a "short course" as recommended by the NHTS. Both answers were no.
- Reaction Time/False Start Combination - The officer was older (50-60ish). The average simple reaction time for a male of that age to a visual stimulus is roughly .325 seconds. Obviously, one might think an operator would be late to start and late to finish giving the same net result - not so fast. Professional athletes are highly trained/disciplined individuals. Offensive lineman in football, swimmers, and track and field stars all occasionally false start. The average NFL football game in 2008 had 2.55 false starts. Should be able to get the cop to admit it is possible that he could have false started - although I doubt any officer will...
- Combination of unknown distance and possibility of reaction time/false start creates potential for over 30% error; in which case my speed recorded at 49.1 on another day could have been recorded at 34.37 or anywhere in between (and probably further out). Given that information and the possibility that the evidence should have shown that I was doing no more than 10 MPH over, the case should be dismissed according to PA 3368 (c) (4) - "No person may be convicted upon evidence obtained through the use of devices authorized by paragraphs (2) and (3) unless the speed recorded is six or more miles per hour in excess of the legal speed limit. Furthermore, no person may be convicted upon evidence obtained through the use of devices authorized by paragraph (3) in an area where the legal speed limit is less than 55 miles per hour if the speed recorded is less than ten miles per hour in excess of the legal speed limit. This paragraph shall not apply to evidence obtained through the use of devices authorized by paragraph (2) or (3) within a school zone or an active work zone."
- Technicalities - I reviewed the documents the officer brought to the court room - all items were originals and not copies and everything was up to date.
So, I think that's roughly it. Sorry for the long post, hope this helps...
10. Der, Geoff & Deary, Ian, "Age and Sex Differences in Reaction Time in Adulthood: Results From the United Kingdom Health and Lifestyle Survey", Psychology and Aging; 2006 Vol 21, No 1, 62-73
Note - I am not a lawyer and am not offering legal advice.