"Police do not use the factory speedo."
These days, police may not use the factory speedo to monitor other vehicles speeds. However police issue vehicles from approx 1984 to at least Commodore VS (and equivalent Falcon) all had "police speedos" fitted in place of the standard poverty speedo the rest of us use.
The "police speedos" featured higher precision internals, apparently better illumination and speed graduations to 2 kmh rather, than 5kmh.
These are still currently available brand new at your GM dealer for VR and VS Commodores (not sure about the other models).
Interesting that the highest accuracy speedos that police used to use in the old days, no longer cuts it these days.
The caper of measuring speed precision to within 1 kmh can be interpreted as nothing more than blatant revenue raising by a desperate state government who acknowledges the state is broke and wishes to punish the humble motorist en masse for the most minor "offences".
Unfortunately, otherwise well meaning paid public servants who administer the law are "conditioned" by their superiors to believe that they are assisting society by nabbing the poor motorist for an "offence" that the majority of us have absolutely no method to properly defend, even if the motorist completely believes he was driving and operating his vehicle within the "law".