The Crown Prosecution Service (CPS) is appealing against a decision to clear a policeman of dangerous driving after he reached 159mph in a patrol car.
Pc Mark Milton argued that he was getting used to a new car
Pc Mark Milton, 38, from Telford, Shropshire, was also cleared of speeding at Ludlow Magistrates' Court.
The officer was captured by the vehicle's video camera on the M54 in December 2003. His defence was that he was testing a new car.
The CPS have not said why they are opposed to last month's verdict.
District Judge Bruce Morgan acquitted Pc Milton on 18 May, calling him the "creme de la creme" of police drivers.
The court heard that the officer was recorded travelling at 159mph on the motorway near Telford in the early hours of 5 December 2003.
In reaching his verdict, Mr Morgan noted that two police officers who gave evidence for the prosecution, including West Mercia Police's senior driving instructor, had declined to classify the defendant's driving as dangerous.
The verdict was met with opposition from road safety campaigners who argued that such a speed could never be justified.