Training is key in radar use

Legends abound about police radar guns picking up mailboxes going 50 miles per hour. But does that really happen? It might, if the officer using the gun isn't properly trained on signal interference.

"I can point a radar detector directly at my air conditioner in my car and get a reading" from the fan, said Kevin Morrison, a public-safety product specialist with Decatur Electronics, the country's oldest maker of radar guns.

We began our discussion of the speed-detection devices last week with a short primer on how they function. This week, we examine the ways, however unlikely, that they can malfunction, as well as your chances of appealing a radar gun reading.

"Weather can cut down on the radar's range because rain obscures some of the radar signal," Morrison said. As a result, you probably won't encounter many speed traps in a downpour.

As mentioned, seemingly inanimate objects, such as your car's fan, can screw up the machine, too.

But police are (or should be) trained to watch out for such problems. The easiest way to check for interference is by listening to the high-pitched whistling sound the radar gun makes, Morrison said. If the sound, known as an "audio Doppler tone," rises and falls smoothly, there's no interference. "If it's broken and raspy, it's not a clear return. It's not a good signal coming in," he said. The officer should be able to testify in court about the clarity of the gun's sound.

But how does he or she know that you're the one speeding, as opposed to the car in front of you or next to you? Morrison said this is another reason why the officer must see you speeding, as the gun, even when pointed in your direction, may be registering someone else's speed.

"It depends on the reflectivity of the target. The gun gets all these signals at a time, and it picks the strongest signal," he said.

"I've had reporters ask, 'Doesn't that mean a semi gives a better return signal, and is more likely to be picked up by the gun?' Yep, it does. But they shouldn't be speeding, either."

An officer, given sufficient experience, should be able to visually estimate your car's speed within 5 miles per hour. If the gun reading isn't close to the visual estimate, the officer should know that the gun was picking up someone else's car, Morrison said.

"Radar readings are used to corroborate troopers' observations of vehicle speeds," concurred David Procopio, a spokesman for the Massachusetts State Police. "A trooper will estimate a speed upon observation based on his training and expertise, and corroborate the speed with the radar unit. Citations are issued at the discretion of the trooper."

Diane McNamara, a Boston reader who groused about a speeding ticket in last week's column, asked how often radar guns malfunction. The answer is, very infrequently. Police know this because they typically test a gun's accuracy every time they use it.

"Per State Police policy, troopers check the calibration on the units at the beginning and end of every shift, and periodically if needed," said Procopio. "If the calibration check determines that the unit is not working properly, policy mandates that the unit be taken out of service immediately until it is repaired."

The easiest way to test a machine, Morrison said, is with a simple tuning fork. The radar gun emits a radio frequency that hits your car and bounces back. The frequency is measured in "number of cycles" per second. Decatur (and other manufacturers) sell tuning forks to police departments that vibrate at a predetermined number of cycles per second. For example, a tuning fork that vibrates 4,320 times per second should produce a reading of 60 miles per hour when the radar gun is pointed at it. If it doesn't, something's off.

The State Police, in addition, has all of its speed guns calibrated annually by an outside company, Procopio said. (Local police departments have their own maintenance schedules.)

Morrison said that his company's radar guns, as well as those made by reputable competitors, are approved by the International Association of Chiefs of Police, which conducts testing on various models. The federal government won't provide any police department with funds to purchase guns that aren't IACP approved, he said.

Before joining Decatur Electronics, Morrison was a Florida police officer for more than 20 years, and an instructor on radar guns for 10.

He's well aware that drivers are often skeptical of speed guns, but given the testing and technology that goes into them, Morrison said, he believes they give accurate readings nearly 100 percent of the time.

Drivers who think they weren't going as fast as the gun's reading sometimes don't take into account their own reaction time, he said.

"A lot of drivers are being very sincere when they say they were not speeding," he said. "Most drivers I caught were speeding a quarter a mile away from me. By the time they saw me they had slowed down. Usually, the reaction process is you see me, you slow down, then you look at your speedometer."

Still, Morrison never begrudged anyone who appealed a ticket.

"If they need to, go to court and see that the officer did all the things he was supposed to do," he said. "I lost my share in court, it didn't happen very often, most of the time it had to do with certification paperwork for the radar unit. I don't recall any situation where I wrote a ticket and it was wrong, but I understand with human nature it's possible to get the wrong car."

What advice do we have for appealing a speeding ticket? According to Charles McGowan, a Charlestown lawyer and a former hearings officer for the Registry of Motor Vehicles, you can certainly ask whether the radar gun was properly tested, when it was last calibrated, whether it was set up in a proper location with proper sightlines, whether the officer was properly trained and whether the officer's observations matched that of the gun.

What you don't want to do, McGowan said, is strut into court and accuse the officer of making a mistake.

"You can attack the machine, the time of day, the lighting. If you're headed east on the Mass. Pike and he is looking west, then maybe the sun is in his eye," he said. "You do not attack that officer. He's doing his job. He's not pointing the gun at Mary O'Brien from Tewksbury driving a green Chevy. He's just pointing it at a green Chevy."

Anyway, the officer who appears at the hearing is unlikely to be the one who gave you the ticket, McGowan added. Usually, a police agency will assign one officer to represent the force in all of the day's court cases.

McGowan's other strategy? Just be polite.

"If you're polite to the clerk and you have no priors, the clerk can find you not responsible," he said, meaning the ticket gets dismissed.

"I was in Stoughton court once. There was an engineer, he'd downloaded 75 pages on radar from the Internet. It was like he knew more about it than anybody there. He was so obnoxious - he kept asking question after question. The judge just said, 'Are you through, now? Good. $175 fine. Next case.'

"That was a lesson to me."