Thursday, June 10, 2010

Wronged by Radar

There's a recurring theme on forums and newsgroups whenever someone posts a missive relating the circumstances of a speeding ticket. Without exception, eventually a Safety Nannny ventures this opinion: "Don't speed and you won't get a ticket." And like a lot of opinions on the Internet, this one is dead wrong.

I routinely hear from defense attorneys shopping for an expert witness for a speeding case. Most involve radar and in most cases, I'm not interested. After a conversation with the defendant it's usually clear that A) They're guilty as charged and, B) Mounting a proper defense would cost perhaps 20 times more than the price of the ticket. After this is made clear, most disappear.

But not always. Occasionally, after scrutinizing the facts of the case, it's obvious that the police officer made a mistake. Sometimes they lie. And over the past decade these cases have often shared two common characteristics: the officer was using moving radar in Fastest Speed mode and the radar involved was a Stalker Dual or DSR model.

The most recent of these occurred late last year when Marc Berger called from California. He'd been cited by the California Highway Patrol for driving 91 mph in a 65 mph zone in the northeastern part of the state.

He was outraged, convinced that his black Porsche Cayenne Turbo, moving at 65 mph, he claimed, had been singled out solely because it was a Porsche. He'd requested a Trial by Written Declaration, a California oddity where both sides present written accounts of the event and a judge makes a determination. After inquiring about the facts of the case I told Berger I'd look into it.

From Berger's description of the event I was fairly certain the radar was a Stalker Dual SL and that the officer had incorrectly identified the vehicle producing the 91 mph target speed. When the case documents arrived, it took about two minutes to determine that I'd guessed right.

The written declaration from the CHP officer, identified as K. Miller, made for interesting reading. It was the standard boilerplate used by speed cops everywhere and began:

"On 08-15-2009 at approximately 0942 hours, I was on patrol in a marked black and white CHP patrol vehicle (#1288901), in full CHP uniform. Traffic was light at the time. The weather was clear and the pavement was dry. I was on patrol driving northbound on US-395 south of Coso rest stop in the county of Inyo. There are four lanes for traffic, two for S/B and two for N/B separted by a dirt/grass center divide. In this section of US-395 there is a posted maximum speed limit of 65 MPH. I was using a Stalker Dual radar unit (#046167), which I have been certified in using, to confirm my speed estimations... The radar was being used in moving, opposite mode with the "fast" mode selected.

I observed a solo vehicle, later identified as a black Porsche Cayenne, traveling S/B in the #1 lane approaching me at a high rate of speed. I visually estimated the vehicle to be traveling at 90 mph. I activated the forward antenna on the radar unit and observed a speed of 91 mph in the target window. I then locked in a speed of 91 mph. There was a strong Doppler sound indicating a good lock on the vehicle being tracked.

The suspect vehicle was rapidly overtaking another vehicle approximately 700 feet in front of it and outside the radar cone. I performed a U-turn and began to oertake the suspect vehicle. I then activated my patrol vehicle's emergency lights and suspect vehicle slowed to the right shoulder..."

Other documents revealed that the officer claimed to have observed the speeding Porsche for 3 to 5 seconds, establishing a proper tracking history before taking enforcement action. I also learned that he had graduated from the academy four months previously, giving him no more than four months, at most, of radar experience. There were over a dozen more pages attached, copies of the radar repair logs, patrol vehicle speedometer accuracy certification and the officer's daily log. None of this interested me; the officer had already proven the case for the defendant.

From the officer's sworn declaration I already knew that A) He'd incorrectly identified the Porsche as the vehicle producing the 91 mph reading, 2) His knowledge of radar operation and particularly, his knowledge of the Stalker Dual, was abysmal, and 3) In his declaration, he was lying about what he'd observed and how he'd used the radar.

The rookie officer may have, as he claims, instantly and with phenomenal accuracy visually estimated a distant vehicle's speed within 1 mph of its actual speed. Veteran traffic officers can visually estimate speeds with an accuracy tolerance of plus/minus 2-3 mph, but In 25 years of operating radar, I've yet to meet a rookie who can accomplish this feat. But to be charitable, let's assume that he did.

What proves the case for the defendant is the officer's statement that he "... observed a speed of 91 mph in the target window... then locked in a speed of 91 mph." No he didn't. The radar won't permit this.

First, some background to support this statement. Among other qualifications, I'm the only person who has ever field-tested all of the frontline moving radar units, the Stalker Dual included. These tests were performed for the manufacturers, curious to see how their wares compared to the competitions'. The Fastest Speed feature was tested extensively during the course of these tests.

I've also worked traffic with the Stalker Dual since 1994 and have owned one for years. And as any experienced Stalker operator knows, the Dual SL and Dual DSR have the longest range in the business. The Stalker can easily clock a Cayenne-sized target at one mile or more; I've clocked 18-wheelers at twice that distance.

Here's an excerpt from my expert report sent Berger that explains what happened:

Radar operating in conventional Moving Mode/Opposite Lane will display only the speed of the strongest target. When two or more targets of roughly similar size are in the beam, the strongest target will be the vehicle in the radar beam that is closest to the radar antenna.

The Stalker Dual has Fastest Speed mode, in which it displays the speed of the fastest vehicle in the radar beam as well as that of the strongest target. Officer Miller was operating his Stalker radar in this mode, monitoring opposite-lane vehicles as they approached his rolling cruiser.

The Fastest Speed feature is designed to enable the officer to monitor the speed of a vehicle that is moving faster than the strongest (generally the closest) target. The speed of the fastest vehicle cannot otherwise be clocked because the more distant vehicle presents a substantially weaker radar return signal.

This reflects a phenomenon known as the radar Inverse Square Rule: Return-signal strength decreases by the square of the distance. For instance, the return signal of a Porsche Cayenne that was at least 800 feet from the radar would be no more than 1/16th as strong as the return signal from a mid-sized passenger car that was 200 feet from the radar. To become the strongest target, the Porsche's frontal area would need to be more than 16 times larger than the closer car's, roughly equivalent to three 18-wheelers sitting abreast of one another.

In his declaration Officer Miller states: "I activated the forward antenna on the radar unit and observed a speed of 91 mph in the target window. I then locked in a speed of 91 mph." [emphasis added]

This 91 mph target-speed reading could only have been produced by a vehicle other than the defendant's Porsche Cayenne. Here's why.

  • If the Porsche had been the 91 mph Fastest target, its speed would have appeared in the Stalker's Fastest (middle) speed display window. Only a target that is both strongest (closest) and fastest can appear in the Target window.

  • As an additional safeguard, the speed of a Fastest target can only be locked when it's also the Strongest target. In the officer's declaration he states that he observed the Fastest speed in the Target window and that it remained there when he locked the speed. Because of the Stalker's design, the only circumstance under which this can occur is when a Fastest speed is generated by the strongest (closest) target. The manufacturer built-in this safeguard to prevent an officer using Fastest Speed from mistakenly assuming that a nearby vehicle is producing the Fastest speed--when the radar instead is reading a vehicle up to one mile behind it.

Bottom line: the rookie officer failed to obtain a proper tracking history of the 91 mph target, incorrectly assumed that the speed of a much closer vehicle wouldn't be read by his radar and assumed that the Porsche must have been generating the 91 mph reading. This tells me that Officer Miller is also not telling the truth when he claims to have visually estimated the Porsche's speed at 90 mph. If he'd been paying attention, he'd have noted that the car he was about to meet was traveling at 91 mph, not the Porsche, and that the nearby car was the only target in the radar beam that was both closest (strongest) and fastest. The radar confirmed that.

Naturally you'll be shocked to learn that the judge ruled in favor of the prosecution. Now Berger is pondering whether to pay the $384 fine or spend big bucks to vindicate himself. By coincidence, I was retained not long before this as an expert witness by a Florida millionaire who'd been nailed by the Florida Highway Patrol in an identical case. The radar in question: a Stalker Dual SL.

Still feel that a radar detector is unnecessary if you drive the speed limit?