Odd Officer behavior at traffic stop

[spdrcr]

I was recently driving the posted limit (scouts honor) when an officer driving the opposite direction had sped up way out in the distance, then dropped right back down again some ten car lengths away. The officer continued to go by, but soon slowed to allow a u-turn and pull me over.
The the words to come from him were "did you know you were speeding you were going 68?" all in one canned sentence. He was VERY willing to allow me to exit my vehicle and view the radar apparatus, which I've never had happen before, on an empty long stretch of country road.

I have figured out what happened, since I was in fact driving the posted limit of 55; he must have slammed on the brakes to manipulate the readings between the cruiser's speed and the speed of my vehicle somehow.
This really pisses me off, since I've come to know this office of the law to be fair, and forthcoming. I am now willing to spend more than the ticket to quash this.

Any ideas, suggestions?

[blewis]

he must have slammed on the brakes to manipulate the readings between the cruiser's speed and the speed of my vehicle somehow.

Hmmm, you're suggesting that the officer somehow was able to change his speed so that the reading that reflects YOUR speed was affected, causing your speed to appear to be 13 mph faster than you were actually going?

I'm not familiar with ANY radar that would react like that. The problem is that the sampling rate is so fast, the officer could not do ANYTHING to affect the result. Of course, I'm not familiar with every radar out there, but most work pretty much the same.

Moving radar, using the doppler principle, uses two beams, one that monitors the right side of the road (from which to calculate the patrol car's speed) and one that's aimed down the road. The beam that's aimed down the road is used to calculate the "closing rate" -- the speed at which your vehicle is approaching the patrol car. The patrol speed, from the second beam, is then subtracted from the closing rate -- and, viola, your speed.

The sampling rate on most radars is around 250 milliseconds. That's how long it takes to "lock" you up and compute the closing rate and the patrol speed. They continue sampling at around 3 samples per second. So, if the officer "slammed" the breaks, the only thing that would affect the readings is the reduction in the patrol car's speed that can occur in 250 milliseconds -- NOT MUCH! It takes many seconds to reduce a car's speed by 13 mph. Even if you locked up the brakes, 2 - 3 seconds. So the reduction in one-forth of a second is not much -- maybe one mph at most.

But, let's look at what would happen. Say you're cruising along at 55 and a patrol car coming the opposite way is flying at 75. Since the closing rate of the two vehicles is 130 mph, his display will show your speed as 55 and his patrol car as 75. Now, he slams on the brakes. His speed drops, let's say as an extreme case, 5 mph in 250 milliseconds (at that deceleration, that means he would come to a complete stop in under 4 seconds -- totally impossible, but we're using an extreme case here to make a point).

So, after 250 milliseconds his speed has dropped to 70. The radar beam monitoring the patrol speed will compute an "average" speed over the 250 milliseconds -- 75 at the start, 70 at the end, so 72.5 mph. The radar monitoring the closing rate will compute the "average" closing rate over the same 250 milliseconds (130 at the start, 125 at the end, thus 127.5). Therefore the display will show a patrol speed of 72.5 (a 3.5% error) -- but your speed will still show up as 55!!! As sampling continues, the patrol speed would continue to drop, but your speed would remain 55.

As you can see, the only inaccuracy is in the patrol speed. But that error has NO AFFECT ON YOUR SPEED display. Bottom line -- there's not much an officer can do with his vehicle that would cause an erroneous reading reflecting a higher speed for your vehicle.

You need to try another strategy. Good luck,
Barry

[spdrcr]

I understand modern electronics, I'm just sure that my speed was 55, and not anywhere near the 68 that he claimed.
Perhaps the sampling was done elsewhere? Not sure if that is even possible.
Kangaroo court here I come...

[blewis]

Sorry, didn't mean to sound condescending. But your statement that, "he must have slammed on the brakes to manipulate the readings between the cruiser's speed and the speed of my vehicle somehow...." indicated (to me, at least) a lack of knowledge of modern electronics.

You didn't post what state you are in, so there's a chance that the officer won't show up. If that's a requirement in your state (it's not in WA), you may get off.

Good luck,
Barry

[Bookm]

Perhaps this is why, in order for radar evidence to receive judicial notice, it is a requirement of the prosecution to produce original copies of the radar calibration records (as well as the tuning fork calibration records), matched by serial no. to the radar gun used that day, which clearly documents the accuracy of the speed measuring equipment, within required time limits.

I read law enforcement forums where officers laugh at this line of defence, but if a guy is certain he wasn't speeding (even if his nic is speedracer, LOL), then surely miscalibration IS a possibility. It's apparent the ONLY evidence is the radar reading. An independant VISUAL estimate was not discussed. Most guidelines I've read REQUIRE the radar reading be concidered only AFTER a visual estimate is made.

Book

[spdrcr]

I was thinking that considering the timeline of events, that the indicated speed would have read sooner on the equipment than it appeared to have based upon the officers actions. He had reduced his speed in two distinct points, the last one having been well after he'd passed my vehicle. He was very focused on the equipment the whole time as well, looking away only briefly to watch the road. Maybe the equipment functions differently from a cold start-up?
I used a comical screen name for the forum, then only hoped that someone would take me seriously; thanks for the info and responses, and I am in WA state.
I have also read some of the previous threads by blewis, which went over the recent changes in our courts here regarding these matters.

[panther10758]

Even if your "theory" has some value I doubt you can get it to hol dup in court. You have no evidence only a theory! As an earlier posted showed your theory doesnt seem valid. If you were to challange this ticket and force a jury trial then judge would likely throw the book at you once you lost and again its VERY doubtful you would win with a defense that is nothing more than a theory

[blewis]

Panther, Washington state is unique in many respects. Most infractions are "civil" in nature, not "criminal". Therefore, you are not entitled to a court-appointed attorney, you are not entitled to a jury trial, and the prosecutor only has to show you are guilty by a "preponderance of the evidence", not "beyond a reasonable doubt."

All in all, Speedracer, your best alternative will probably be deferred findings. If you haven't done that in the past seven years, it's a good way to go. At least it keeps the offense off your record.

Barry

[moburkes]

Speedracer, I'm not sure how you could have seen all of this, if your eyes were on the road ahead of you:

He had reduced his speed in two distinct points, the last one having been well after he'd passed my vehicle. He was very focused on the equipment the whole time as well, looking away only briefly to watch the road.