§ Lord Monson
asked Her Majesty's Government:
Whether it is an offence to drive or ride a motor vehicle after taking medicinal drugs which affect the central nervous system (found by the Transport and Road Research Laboratory to be a factor in 5.6 per cent. of fatal road accidents), and, if so, whether the presence of such drugs can be detected by any modified version of the breathalyser.
§ Viscount Davidson
A person who drives or attempts to drive a motor vehicle on a road or other public place when unfit to drive through drink or drugs is guilty of an offence under Section 4(1) of the Road Traffic Act 1988. The presence of medicinal drugs which affect the central nervous system cannot generally be detected by breath testing. A person suspected of being unfit to drive through drugs may be required to provide a specimen of blood or urine for analysis.