Instruments Used to Catch Speeding Drivers in Fairfax

In order to catch speeding drivers in Fairfax, law enforcement officers employ a variety of methods including radar guns, LIDAR devices, speed traps, traffic cameras, and pacing. Below, a Fairfax speeding ticket lawyer discusses what you should know about these methods, and whether there are any defenses if you are issued a speeding citation.

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Radar Guns and LIDAR Devices

Radar guns and LIDAR devices are both very frequently used in speeding cases, and are the most well known among drivers. Both are considered to be very accurate when properly calibrated, especially LIDAR devices which are newer and use a laser instead of a doppler radar.

Additionally, both of these devices, due to their extreme accuracy, are given a lot of weight in court as long as the law enforcement officer can provide that the device was properly calibrated. Typically this is done by providing a certificate that shows the equipment was properly calibrated. In general, stationary radar is most accurate than moving radar, however both are given serious weight in court and not often reduced.

Fairfax Defenses For Radar and LIDAR Devices

There are a variety of factors that can go into creating a defense for radar or LIDAR readings. For example, if a reading happens on a bridge, wind and other factors may impair the proper functioning of of the radar. The officer also has to demonstrate that the radar was properly calibrated and has to have a certificate showing this, which requires particular information being included. For improper or lack of recent calibration of the gun, this is definitely a defense. The officer must testify as to the recent calibration of the equipment and must have the calibration certificate as well.

Virginia code sec. 46.2-882 states that a calibration certificate complies if:

  1. It was an original or true copy,
  2. It shows when and by whom it was made and
  3. The testing certified to was conducted within the six months prior to the date of the offense.

If any of these requirements are not met by the officer than the calibration is not considered to be reliable and will not be admissible in court.

Other Issues With Radar Guns and LIDAR Devices

User error is an issue that can come up in regards to relevancy of the result of the radar or laser unit particularly when there are many cars in the road driving closely together as happens commonly with traffic. On the highway, drivers may drive in groups, which can cause these issues. Police officers often keep quite a  distance from the driver they’re targeting in order to not be detected.

This is especially common when the officer is using Lidar. If there’s any movement by the officer of the Lidar equipment when he uses it to detect the driver’s speed, the LIDAR can mistakenly result in a 10 to 20-difference in distance from a target that’s actually a thousand feet away which means that it’s possible the result was actually coming from a different car.


Pacing is when an officer follows the vehicle and maintains a constant distance between the police officer’s vehicle and the driver’s vehicle for a period of time long enough to make a reasonably accurate estimate of the driver’s speed by the officer’s speedometer.

Pacing is admissible evidence of speeding and is readily accepted by the court, however, just like radar and LIDAR, pacing has its own requirement of having a calibration certificate of the officer’s speedometer to show that his speedometer was working properly. With that said, there are a lot of issues with this because unlike radar and LIDAR, it’s a lot more subjective.

The officer has to determine the speed just by looking at his speedometer rather than having equipment that does it automatically. The officer is human and therefore prone to human error.  It’s possible in these kinds of cases that the officer was gaining speed as he was targeting vehicle because he had the intention of pulling him over, which would mean that the speed that he determined that the targeted vehicle was going is actually higher than the actual speed that the vehicle was going.

There is also the risk that the officer’s own speedometer was incorrect, which if he doesn’t have a calibration certificate, is an easy case to have thrown away. It’s very important to take apart the officer’s testimony to determine that he paced the vehicle exactly as the procedure requires him to do so.

Common Myths About Speed Reading Instruments

One of the common myths about speeding instruments in Fairfax is that if you ask the officer to show you the reading on the instrument, he is required to show you. There is actually no law that says this and therefore no requirement that the police officer has to show you anything of his equipment.  Sometimes, police officers comply and they will show you, but it’s not a requirement whatsoever.

Another common myth is that it’s easy to argue in court that the radar equipment or LIDAR equipment locked on to the wrong object. In fact, this is really hard to prove. It may be the case that the police officer did lock on to the wrong object, but without a very strong cross examination and getting the police officer to admit openly that there is a possibility that the way he did his job was incorrect, this is not a very strong defense.