On channel 7s Today tonight they had a bit about highway patrol that book people speeding with no real evidence that is needed to be provided in court.
Some of these rules are for your case to be valid
1. They must be locked on to your vehicle for 3 seconds while your speeding
2. The car must be stopped while locked on to your vehicle
3. There can't be any cars around you.
4. If you are caught speeding you must have that "you are now being taped" speech by the copper or then its not valid