In Ontario, speeding tickets are very hard to beat because the caselaw basically allows the Justice of the Peace and the Judge to simply accept what the officer says as fact. If the officer says you were speeding, then it must be true! If the officer says they were trained on the Radar or Lidar device, then it must be true! If the officer says the device was working properly at the time, then it must be true! Of course we know that just because the officer believes the Radar or Lidar was working properly, does not mean it actually was. With an expert witness, you can then challenge the credibility of the officers statements and bring evidence that shows the device may not have been accurate at the time it was used.
You should also read the following post on why you need an Expert Witness: Caselaw regarding the need for an Expert Witness