No they dont. Circumstantial and witness evidence are sufficient. They need to have enough evidence to convince a judge (or jury if you want to spend enough money to push it that far) that you are guilty beyond reasonable doubt. This doesnt need to be a speed reading. A coppers word against yours, a coppers has much more weight. Your past record is a factor too, if you have been done on previous occasions for similar offenses, it will make the judge likely to believe you did it again.
A copper becomes 'an expert witness' and his evidence will be considered as such by a judge. If the copper doesnt have radar proof, he will offer his 'expert opinion' to state that in his opinion, based on his years as a traffic cop and thousands of people whose speed he has actually measured, your speed was between X and Y.
Your charge may not be X.kmh in a Y zone, it may be modified to something non speed specific like dangerous driving or driving without due care. Funnily enough, these charges usually carry higher penalties, but are harder to disprove as they dont require a speed reading.
You then need to discredit the copper in the judges eyes, creating 'reasonable doubt'. Yeah you could try telling the judge you were being harassed because you behaved like a dick to the copper. Thats a silly approach, it will make no friend out of the judge. Unless you can present proof of a dozen instances in the last month of the same copper giving you grief, a harassment defence is a waste of time.
What you want to do is be charged with speeding, its the lesser of the available evils. The best approach is to admit to the judge that you were speeding but you dont believe you were going as fast as the copper claims... in other words, tell the truth. If you are lucky, the judge will decide to find you guilty of the lower speed, since you have co-operated.
Your only other chance is that if you get a chance to speak to the prosecutor prior to trial, tell him you will be pleading not guilty and why. He may choose to lower the speed in return for your pleading guilty, or he may decide its just not worth proceeding with and drop it. Or he may just leave the charge stand as it is if he thinks he can win.
The system can be beaten, but often its harder and much more expensive than its worth. Its all very well crying foul but its an imperfect system. Just think of it as karma for previous offenses that you got away with and suck it up sunshine. Learn from the experience.
