10Detention of persons affected by alcohol or a drug
(1)Subject to subsections (2) and (3) below, a person required to provide a specimen of breath, blood or urine may afterwards be detained at a police station until it appears to the constable that, were that person then driving or attempting to drive a motor vehicle on a road, he would not be committing an offence under section 4 or 5 of this Act.
(2)A person shall not be detained in pursuance of this section if it appears to a constable that there is no likelihood of his driving or attempting to drive a motor 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.
(3)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.