RADAR, SPEED-MEASURING DEVICE
Speeding and Radars
Radar, or Radio Detection and Ranging, allows police to determine the rate of speed of a vehicle through the Doppler Effect before writing up speeding tickets. A radar gun sends out a beam of electromagnetic waves at one frequency, and when the waves encounter a vehicle, they are reflected back to the officer at a different frequency. The change in the frequency of these waves is referred to as the Doppler Effect, and is interpreted as a speed calculation to the officer operating the radar speed-measuring device.
Radar speed-measuring devices can be used in a stationary or moving position. In stationary mode, the officer and the radar gun stay in one place and capture the rate of speed of suspected violators as they drive past. In moving position, the officer and the speed radar are moving through traffic. This type of radar speed-measuring device is often affixed to police vehicles, while the stationary type is a hand-held piece of equipment like a gun. If the officer is using the radar speed-measuring device in a transitory manner, he is required to check the recorded speed of the target vehicle against his own speedometer to ensure that the reading is accurate before writing a speeding ticket. While they may not match up exactly, the separate speed readings should be close.
Speed radar is the most widely accepted and widely used form of measuring speed for speeding tickets. However, it is not infallible. Similar to the beam from a flashlight, radar waves spread out as they get farther away from their source. This means that the radar gun may be detecting other traffic and giving the officer an inaccurate reading of the target vehicle's speed. Radar speed-measuring devices are also subject to interference, resulting in a distortion of the reading. Billboards, large metal signs, neon signs and buildings can impair the ability of radar to obtain an accurate reading, sometimes resulting in speeding tickets being given out incorrectly.
To ensure that, barring any interference, readings taken by the radar gun are not faulty, they must be properly calibrated and checked by police officers prior to beginning their shift and after finishing it. Tuning forks are used to check the accuracy of the radar speed-measuring device, and many models have internal calibration systems. The accompanying manuals provide the recommended methods of calibrating and testing the radar gun. Officers commonly check the accuracy of their radar guns by comparing them against a certified calibrated speedometer, or against another radar speed-measuring device, to ensure that they display the same readings.
When charging someone with a speeding offence, the prosecution must be able to prove the accuracy and reliability of the radar speed-measuring device used to obtain the speed reading in question. If they cannot do this, the charge may be thrown out. To do this, the prosecution must be able to show that the officer was properly trained on how to operate and test the radar gun before writing the speeding ticket. In the case of R. v. Hawkins, 2009 ONCJ 101 the judge found that the manufacturer's tests of the radar gun are required tests to be performed by the operator on every occasion before it is used. Because the prosecutor could not prove that these accuracy tests had been carried out, the court was left with reasonable doubt as to the accuracy of the speed, and the charge was dismissed.
The issue of testing radar speed-measuring devices is raised again in R. v. Soungie  O.J. No. 2338. Soungie was charged with speeding, as determined by an officer operating a radar gun. On direct examination, the officer testified that he tested his radar gun before using it and after his shift, but on cross-examination the officer testified that he performed the recommended tests before his shift only, not after. The justice found that the discrepancy in the officer's testimony created reasonable doubt as to the accuracy of the radar gun used, and Soungie was acquitted.