Detention of persons affected by alcohol or a drugN.I.
21.—(1) Subject to paragraphs (2) and (3), 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 the person then driving or attempting to drive a mechanically propelled vehicle on a road, he would not be committing an offence under Article 15 or 16.
(2) A person shall not be detained in pursuance of this Article if it appears to a constable that there is no likelihood of his driving or attempting to drive a mechanically 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.
(3) A constable must consult a medical practitioner on any question arising under this Article whether a person's ability to drive properly is or might be impaired through drugs and must act on the medical practitioner's advice.