Linenhall Chambers’ Paulinus Barnes has won an appeal which could have implications for hundreds of motorists convicted of speeding offences.

The prosecution case collapsed at Mold Crown Court after expert evidence cast doubt on the reliability of laser devices when operated through a car windscreen. Paulinus Barnes said: “The very clear guidance from ACPO, the Association of Chief Police Officers, and from the device manufacturers, is that hand-held laser devices should not be operated through glass. Laser devices calculate the speed of a moving vehicle based on the speed of pulses of light between the device and the object but the speed of the light pulse is assumed to be the speed through the atmosphere, and not through glass”.

In this case the police office accepted that he had directed a laser device at the driver’s car through the windscreen of his police vehicle. The driver’s conviction and fine of £250 was quashed by the court at Mold after the prosecution accepted that there were doubts as to speed calculated by the device.

Paulinus Barnes was instructed in the case by MAJ Law Solicitors of Widnes