Dash Cam And GPS Prove Laser Gun Was Inaccurate

[erkme73]

A year or so ago, I saw an article on a new technology which allowed business owners to install a small unobtrusive video camera on the mirror in their vehicles (www.drivecam.com). The camera constantly records the view out the front windshield (and optionally rearward into the vehicle) – looping every 20 seconds. When the camera sensed shock (such as impact from an accident) it would save the 10 seconds leading up to the accident, and the 10 seconds following the accident. Their website has some pretty interesting videos. Anyway, I wanted one for my personal vehicle. Unfortunately, Drivecam only sells to fleet vehicle businesses.

So, about 6 months ago, I started building my own with commercially available parts. I now have a camera, digital video recorder, and video monitor installed in my truck. The camera records to memory, and only when the vehicle is in motion (or there is motion in front of the truck). Not long after installing the system, I thought it would be even better if the speed and heading were imprinted on the video somehow. So, I installed a GPS and video overlay unit. Technical, yes, but here’s what it does… When I drive, I have a permanent recording of what is in front of me, stamped with day, time, speed and heading. It is extremely accurate – since GPS is document to be +/- 0.1 MPH.

Here’s where it get interesting… In mid-February of this year, I was stopped by a Pasco Deputy using a laser gun. When he pulled me over, he asked me “do you know how fast you were going”. Nervous, and not thinking about the video system, I said “No.” He told me 72 MPH (in a 55MPH zone). He then left to write my ticket. In his absence, I remembered the video system. I folded down my sun visor (which hides the video monitor) and backed the video up a few minutes. Crystal clear was my speed as I approached the Deputy sitting on the side of the road with his laser gun. The GPS recorded speed? 68.3 MPH. When the officer returned, I showed him the video.

“Cool! Our cruisers don’t even have that!”. I then asked him to reduce the fine to match the GPS speed – since it is accurate to 0.1MPH. The Deputy refused, stating that he tests his gun ‘every morning’. We parted ways. I then entered a plea of not-guilty, requesting a court date.

In the mean time, I did a BUNCH of research on both GPS and laser speed detection equipment (aka LIDAR). The most accurate LIDAR equipment is rated (by the manufacturer) at +/- 1.0 MPH (I have the documentation). That’s 10x worse than GPS. Not only that, but the testing of laser equipment falls WAY short of established standards used for radar guns. Laser technology uses distance measurements (unlike radar which uses Doppler/frequency shift). Consequently, if the officer moves as little “the thickness of a human hair” while trying to acquire a speed measurement (a phenomeon known as ‘slipping’), the shift in the laser target (i.e., from front bumper to windshield) will result in a recorded speed considerably faster than actual. This 10 minute British news broadcast points out, scientifically, how such errors happen. The very last quote in the video states “If you’re thinking of contesting a speeding allegation, there is something you should know. The police have told us that anyone who uses the evidence from our film to plead ‘not guilty’ could, if they lose, face a much bigger penalty in court”.

The difference between 68MPH in a 55MPH (13MPH over) and 72MPH in a 55MPH zone (17MPH) is the difference between a minor speeding offense, and a major (15MPH or greater). I have NO problem paying for my actual speed violation. I do, however, have a problem being charged with more than true speed. Especially if it means my insurance is increased or even canceled.

Here’s what it boils down to… How many drivers KNOW exactly how fast they were going when they were pulled over by law enforcement? I would argue very few. And, of those that just happened to know, how many can go to court and PROVE their actual speed? Up until now, ZERO.

The exciting angle on all of this is, I have evidence showing how fast I was going. Courts have taken judicial notice, making GPS technology admissible and acceptable in court cases - see this one.

My court date is TODAY (June 6th). I intend on representing myself, and will show my video to the judge. I’m hoping that this will do more than just draw his/her interest. From a legal/technical standpoint, the case should be dismissed once I’ve proven the State’s equipment to be inaccurate. Unfortunately, by showing my video, I’m admitting to speeding. The best I can hope for is a reduction in speed. An inaccuracy in state equipment (or training), whether intentional or not, represents a huge, unnecessary (and often un-provable) burden on it’s people. In traffic court, it’s your word against a sworn officer of the state. You are presumed guilty unless you can prove the officer wrong. I hope to do just that.

This is a short (and highly compressed) video of the actual offense, followed by a clip showing a radar sign matching my GPS speed. . I’d LOVE to prove my equipment against either radar or laser - which is why I am looking for a helpful cop.

[blewis]

Two comments: First, where did you find a spec for GPS being accurate to .1 MPH? I've never seen anything close to that. And second, your video begins just seconds before seeing the patrol car. Yet, I've seen LIDAR used up to 1500 feet away -- over 1/4 mile. At 60 MPH, you would have still been 15 seconds away! While the video clearly shows (assuming the accuracy of your GPS) that you were, indeed, going 68.3 when you passed the officer, it does not show how fast you were going prior to that. What was the distance when the officer targeted you?

If I were a judge, I could easily see that you could have been doing 72 and slowed to 68 when you saw the officer's vehicle.

Oh, and the cases you cite DO NOT support the admission of GPS as a Speed Measurement Device.

[erkme73]

Thanks for the comments:

GPS accuracy: Garmin manual specification page. The HDOP (horizontal dilution of precision) was 1.1 (virtually perfect), and 10 sats locked. This information will come with me tonight.

The officer wrote on the ticket that he used laser at 600'. At 68MPH, that's 100 feet per second (according to Google). That would be 6 seconds before I am directly parallel to him. That's where the video starts. I have 2 hours of video leading up to the point where I'm pulled over. At no point do I exceed 68.5 mph. I kept the video short so I don't burn the patience of the judge. I have a longer version in case they ask.

Finally, while the 3rd DCA does not specifically mention speed in it's acceptance without a FRYE hearing, it does state that GPS technology is accepted as evidence. That's a broad statement - something I'm hoping the Hearing Officer/Magistrate will accept.

[blewis]

Finally, while the 3rd DCA does not specifically mention speed in it's acceptance without a FRYE hearing, it does state that GPS technology is accepted as evidence. That's a broad statement - something I'm hoping the Hearing Officer/Magistrate will accept.

I think you'll have to cross the same or similar hurtles as a prosecutor trying to admit radar evidence. WA law requires that evidence can only be admitted if a foundation is created. The law allows the court to take judicial notice that radar guns, in general, employ the doppler principal to measure speed when properly calibrated and used. However, the state must also show that this particular radar device was, indeed, properly calibrated and used. These two ingredients provide a foundation for the admission of radar evidence.

The court may take judicial notice that the technology will, within a given tolerance, employ the "time of travel" principal to calculate the location of a GPS device. However, the prosecutor could object to the admission of your evidence as being without proper foundation. You might have to show that your particular GPS device is properly aligned and can be used to calculate speed. Remember, some older GPS units were only good to 100 yards, or so. You might have to show that yours is far more accurate than that.

The update (refresh) rate of the GPS reading 10 satellites is over 1 second. The distance travelled in 1 second at 68 versus 72 is just over 5 feet. Your GPS would have to resolve your location to within 5 feet. How would you prove that?

Anyway, with any luck you'll get a judge who doesn't want to deal with all this and let you off. I've seen it happen more than once.

Good luck,
Barry

[erkme73]

Well, it's over. First officer to show: mine. They dismissed about 75% of the cases. One after another was called, and dismissed w/o explanation. It think the cops wanted to see the final hockey game... Of course, I wasn't one of lucky ones.

I had two options when I faced the Hearing Officer; 1) Keep my plea of not-guilty, and try to prove the officer's equipment was faulty or not used correctly, or 2) change my plea to no-contest.

Option 1 meant even if I had proven my case, the court would have found me guilty of my confessed speed of 68mph. That would have resulted in 3 points adjudication.

Option 2 meant I plead guilty, but would be allowed to provide evidence to mitigate the charges or fines.

I chose option 2. After showing the video, the Hearing Officer dropped the charges to 68, but the paperwork still says I was found guilty with points withheld.

There simply was no way to prove the county's equipment was faulty or inaccurate without setting myself up for conviction of my actual speed. That's only fair. Still, I was hoping there'd be some sort of consequence for the department using 'bad' equipment or technique.

[Bookm]

Here is an example of what I consider to be "the perfect lidar defence". Though this example deals with the presence of a second vehicle, the same arguments could be made but referring to the beam striking various parts of your car (or even a following vehicle through your windshield) resulting in an eroneous speed reading.

The bonus is the summary of the "Radar" wins also that day.

Lidar Win: http://www.radardetector.net/viewtop...25138&start=15
(scroll down 'till you get to "BLK_BNZ" court summary)