Police Use of Radar Guns in Utah

Police officers in Utah commonly use radar guns to determine the speed of a vehicle. In addition to getting a ticket (citation), a driver pulled over for speeding may also be subject to questioning or search relating to other suspected crimes, and may end up facing charges much more serious than a simple speeding ticket.

Before a police officer can extend the scope (subject matter) or duration (length of time) of a basic traffic stop, the officer must first observe some evidence of another crime. Criminal charges including DUI and drug offenses commonly come from evidence obtained during a traffic stop. But if the officer detains or searches a vehicle without the required constitutional evidentiary basis, then evidence obtained as a result of a constitutional violation may be subject to suppression under the Fourth Amendment.

If you are being prosecuted for a crime based on evidence obtained during a traffic stop, it is important to have the assistance of an experienced criminal defense attorney. Contact us today to see how we can help you.

How does a radar gun work?

Speed measurement using radar guns is based on the Doppler effect and measures the change in frequency of radio waves.

Stationary radar guns measure the difference in frequency between the original radio waves emitted by the unit as compared with the waves that reflect back from the object they are trying to measure. If the object is moving, either away from or toward the radar source, the reflected waves will return to the unit at a different frequency (higher or lower depending on whether the object is moving toward or away from the radio wave source).

Imagine yourself standing on the side of a road and listening to traffic as it passes by you. As the cars pass, you will notice the pitch of the engine sound starting out relatively high, and then drop down to a lower pitch as the car passes and begins to move away from you. The faster the car is going, the greater the pitch change will be. (The same principle is used by astronomers looking for redshift and blueshift in light from stars to measure whether a star is moving toward or away from the earth, and measuring how fast.)

For a radar gun mounted in a moving vehicle, the gun has to be able to measure the frequency of two sets of radio waves: 1) the waves reflecting back from the target vehicle; and 2) the waves reflecting from some stationary object, such as the road surface. The difference between those two frequencies is then used to calculate speed.

Because radio waves spread out as they travel away from the radar gun (similar to how radio waves coming from the single point of a radio station's transmitter will spread out to fill an entire valley), it can be difficult to accurately target a specific vehicle in heavy traffic. Accurate targeting becomes more difficult as the distance between the vehicle and the radar gun increases.

Finding a Utah Criminal Defense Attorney

If you are facing criminal prosecution in Utah, the assistance of an experienced attorney can be vital to obtaining a good outcome. A basic traffic stop can turn into an investigation for a much more serious crime that can have serious long-term consequences. As a criminal defense attorney in Utah, Stephen Howard has assisted clients and defended their rights from initial police investigations through jury trial and appeal. His experience includes cases ranging from murder to DUI, and virtually everything in between.

Contact us today to arrange for an initial confidential consultation, and see how we can help you.