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Can I Challenge Radar Gun Evidence in Court?

It is a fairly common sight on our roadways: a law enforcement officer standing by their patrol car aiming a radar gun at oncoming traffic.  Radar guns are useful tools for detecting vehicles exceeding the speed limit, but, like all measurement devices, they have their weaknesses. 

If you have been pulled over for speeding based on the information from a radar gun, it’s possible to challenge the radar gun evidence in court based on the limitations inherent to radar guns.  Any challenge will be an uphill battle, however.

How Radar Guns Work

Radar guns are devices that both send and receive radio signals.  They work by directing a radio signal towards a vehicle, then receiving the same signal as it bounces off the vehicle.  Using what is known as the Doppler Effect, the device can calculate the speed of the vehicle based on changes in the value of the returning signal.

Law enforcement agencies have also begun moving towards Light Detection and Ranging (LIDAR) technology, which operates in much the same way as radar, but using lasers instead of radio waves. 

Regardless of which technology the agency uses, these devices are sensitive tools of measurement that require regular calibration and adjustment.  Radar guns, for example, require the use of a tuning fork to make sure that the device is producing accurate readings.  Manufacturers of the devices recommend calibration before every use, but states may require testing and calibration much less frequently.

Calibration Record Evidence


Some officers may erroneously believe that they can calibrate the radar gun without using the tuning fork, so always ask whether they did in fact use the fork during calibration.  If they did not, it opens up another opportunity for you to argue that the ticket is based on false evidence and should be dismissed.

Radar, LIDAR Training

Most states also require officers using radar or LIDAR technology to go through approved and certified training programs before operating the devices, so check to see if the officer who issued your ticket had the required training.  If not, you can argue that the elevated reading occurred as a result of operator error, and not because you were actually speeding.

None of these arguments will automatically result in the dismissal of your ticket.  If you know for a fact that you weren’t speeding, however, you don’t have to pay the ticket just because the police officer’s radar gun showed that you had exceeded the speed limit.  Radar guns are not infallible, and they can provide incorrect information if not operated or maintained correctly.

Next Steps: Speak to a Traffic Ticket Lawyer

As a licensed driver, you have many rights you may not know about. A skilled traffic ticket attorney will have a wealth of knowledge when it comes to traffic law. He or she can greatly increase your chances of having your ticket reduced or dismissed altogether. Speak to an attorney about your options in your area today. 

Next Steps
Contact a qualified traffic ticket attorney to help
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(e.g., Chicago, IL or 60611)

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