Contesting a Traffic Ticket: Police Laser Gun Accuracy

It’s not unusual for laser gun accuracy to be challenged in the courts. There are several factors considered when determining the accuracy: 

How Laser Guns Work 

Laser guns work by sending pulses of light to an object, in this case, a vehicle. These pulses of light bounce off of the object and back to the laser gun. The change in the distance between the pulses is measured to determine

Laser Gun Challenges

The following are some basis for laser gun challenges:

  • Steadiness. A laser gun has to be held steadily or the measurement will not be accurate – that is, any movement of the gun can affect the reading.
  • Targeting. The gun also has to be held on only one part of the vehicle, usually the front license plate. If the gun is used to measure multiple parts of the vehicle, it will be inaccurate. The error can be anywhere from a few miles per hour up to 60 miles per hour.
  • Precipitation. Laser gun accuracy may also be challenged if the reading occurred during inclement weather.  That’s because it may be argued that the laser is bouncing back from the precipitation, not the vehicle.
  • Calibration. Calibrating a gun can be very important, and depending on the jurisdiction, the calibration can be the basis for contesting a ticket. Some jurisdictions test for accuracy daily, others only do so at various times throughout the year. If a gun has not been calibrated recently, a challenge may be in order to determine the accuracy.
  • Officer Training. If the police officer using the gun has not been trained properly the results can be contested.

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