The magistrates’ were advised that the police device was approved, calibrated and operating correctly (matters not in issue), and that the appellant’s device had none of those features.
The magistrates acquitted on the basis that the GPS tracker cast sufficient doubt as to the correct speed so as to be unable to convict.
The prosecution appealed.
Held: It was clearly established in Cracknell v Willis  A.C. 450 that evidence from approved devices was not conclusive evidence. Having been properly directed it was a matter for the court to weigh up the competing evidence, and it could not be said that the justices decision was perverse or irrational. There was reasonable doubt that M exceeded the 50 mph speed limit.