This is not legal advice and is for informational purposes only.
The purpose of an expert witness is to bring unbiased information to the court so the Justice of the Peace or Judge can make a better informed decision. An expert witness possesses special knowledge and experience going beyond that of the trier of fact. (see R. v. Beland,  2 S.C.R. 398, at paragraph 16).
In Ontario, the courts simply take at face value the officers statement that they are a qualified radar/lidar operator and that they believe the device was working properly at the time, and therefore the speed reading was correct. Even cross-examination of the officer on these points is mostly useless because the court will say “there is no statuatory requirement as to what a qualified operator is, so they say they were trained, so it must be true, and they say it was working properly, so it must be true”.
The only way to you can beat it, is for the defence to put their own expert on the stand who can explain why the device has a very good chance of NOT being accurate (since they are NEVER calibrated in Ontario).
I beleive that for speeding in Ontario caselaw is lacking many crucial facts that it needs, and the following caselaw supports my position on the need for an expert witness in order to bring contradictory evidence.
R v Antunes 2004 ONCJ 352 (appeal)
 …barring any evidence elicited by the defence to challenge that inference.
 The defence was not able to challenge the ofﬁcer’s perception of his speedometers accuracy…
R v Chau  O.J. No. 5508 (appeal)
 …he has no evidence through cross-examination by defence witnesses that would suggest it [the speedometer] was inaccurate…
R v Xu 2012 ONCJ 278 (appeal)
[Page 7] It is also important to remember that contradictory evidence is one of the most important factors to consider in weighing evidence.
[Page 10] There is nothing specific by way of cross-examination or contrary evidence to undermine the officer’s evidence as to the proper functioning of the machine.
[Page 12] …but that the evidence might be shaken on cross-examination or by contrary evidence as to the speed.
[Page 13] …no contrary evidence.
[Page 17] There was no contradictory evidence brought forward by the accused
R v Kleiner 2008 ONCJ 159 (appeal)
[HELD] There was no evidence that cast doubt on the qualiﬁcation of the ofﬁcer as a qualiﬁed radar operator.
 …the defence had presented no evidence to challenge the evidence of the reliability of the radar speedmeter device for identifying the speed of a vehicle on the highway.
 There was no challenge with respect to the accuracy of the tests.
 …there is no evidence that cast doubt on the qualiﬁcation of Constable Marsh as a qualiﬁed radar operator.
ADDITIONAL COMMENTS ON RADAR/LIDAR:
It is a fallacy to believe that just because two things give the same reading, that they must both be accurate. So if checking a radar against a speedometer gives a matching reading, this does not prove that either the radar or the speedometer are accurate. It simply proves that both are equally inaccurate. Only if one of them has been calibrated against a known standard, can you say it is accurate. This is the scientific field of Metrology.
ADDITIONAL COMMENTS ON SPEEDOMETERS:
As a side note, some of these cases above refer to R v Bland 1975 6 OR 2d 54 as the “speedometer caselaw”. There are several problems with R v Bland. The first being that a speedometer holding a steady speed over a certain distance has absolutely NO bearing on whether the speedometer is actually accurate or not. The second is that the quote used is from 1964. And the third is that R v Bland is referring to mechanical speedometers, and since the very early 2000’s all vehicles now use electronic speedometers, which means the speedometer is an electronic device (see note on electronics below).
ADDITIONAL COMMENTS ON ELECTRONICS:
All electronic devices (which include speedometers, radar and lidar) are subject to electronic drift which causes them to become less accurate over time. Electronic devices need to be re-calibrated on a regular basis (1 year is a good recommendation) to make sure they are still within their accuracy range (tolerance). Comparing one un-calibrated device reading to another un-calibrated device reading does not prove accuracy. Checkout the scientific field of Metrology.