LASER, SPEED-MEASURING DEVICE
Speeding and Lasers
Light Amplification by Simulated Emission of Radiation, known as Laser or LIDAR (Light Detection and Ranging) guns, are a newer method used by police to determine rate of speed. This method uses an infrared beam of pulsed laser light, which is emitted at frequencies that allow the beam to be focused in on a very narrow target area. The reading of speed is based on the number of nanoseconds the laser light takes to bounce off of the targeted vehicle and come back to the speed-measuring device before the officer writes a speeding ticket.
Unlike the radar gun, the laser gun is equipped with an eyepiece that allows the officer to view traffic and aim the laser at a specific vehicle. This allows an officer to view individual vehicles within a stream of traffic. A vehicle is targeted by moving the laser speed-measuring device until the laser is positioned at the front of the moving target. The officer then pulls the trigger on the laser speed gun and receives a rate of speed for the targeted vehicle to use in writing speeding tickets.
Laser guns are more effective at short range and must be used from the stationary position. They are usually only used as hand-held versions because trying to use them through the glass of a car window can disrupt the speed laser's range, resulting in inaccurate readings and thus incorrect speeding tickets. They are not known to have problems with interference from any other sources and are thus a very accurate device for measuring vehicle speed. This makes speeding tickets with laser speed-measured readings very difficult to discredit in court, although not impossible. It was accomplished in the case of R. v. Bourne  O.J. No. 2869, in which the defendant was charged with speeding, as determined by the laser gun the officer was operating. While the officer was trained in the use of the speed laser and had tested it in accordance with the manufacturer's instructions, the officer had not performed an independent test by comparing the results to those of a conventional radar speed-measuring device before writing the speeding ticket. The judge found that it was essential that evidence be presented that the device had been tested against conventional speed-measuring devices and found to be accurate, and so allowed Bourne's appeal of her conviction.
The same grounds were used in the case of R. v. Sourlis,  O.J. No. 6274 , in which Sourlis appealed his conviction for speeding on the basis that the Crown had not adequately proven the accuracy of the laser speed-measuring evidence used to convict him on his speeding ticket. Justice of the Peace Leggat ruled that comparisons of the readings from the laser gun against independent technology are required to prove that the laser gun is producing correct readings. There was no testing done within 30 days before or after the reading was taken of Sourlis' speed, and so his conviction was set aside.