[Soundy]

Skidmark will tell you, winning any dispute comes down to your credibility vs. the cop's. It's possible, though not likely, that if the cop makes a lot of "mistakes" like this, or has a history of writing borderline-BS tickets, he may already have damaged credibility with the JP.

The JP may have the train of thought, "If you can't tell a BMW from a Mustang, how can you possibly read a speedometer?" Or remember that the court probably sees the same officers on a regular basis for these disputes, especially if the cop is a jerk that writes a lot of 1km-over-the-limit, walking-and-chewing-gum tickets... a JP might get frustrated with such minor infractions clogging up his court and decide to smack the cop down.

Again, it's not likely... but it's possible.