Subject to subsections (2) and (3) below, a person required F1under section 7 or 7A to provide a specimen of breath, blood or urine may afterwards be detained at a police station F2(or, if the specimen was provided otherwise than at a police station, arrested and taken to and detained at a police station) if a constable has reasonable grounds for believing that, were that person then driving or attempting to drive a F3mechanically propelled vehicle on a road, he would F4commit an offence under section 4 or 5 of this Act.

F5Subsection (1) above does not apply to the person if it ought reasonably to appear to the constable that there is no likelihood of his driving or attempting to drive a F3mechanically propelled vehicle whilst his ability to drive properly is impaired or whilst the proportion of alcohol in his breath, blood or urine exceeds the prescribed limit.

A person who is at a hospital as a patient shall not be arrested and taken from there to a police station in pursuance of this section if it would be prejudicial to his proper care and treatment as a patient.

A constable must consult a medical practitioner on any question arising under this section whether a person’s ability to drive properly is or might be impaired through drugs and must act on the medical practitioner’s advice.