The Supreme Court held that a 20-minute observation period before a breath-test requirement rendered Michael Finn’s detention unlawful because the prosecution had not shown that the wait was reasonably necessary for taking breath specimens.
The ruling, delivered by Murray J on 19 February 2003, arose from a case stated by a Dublin Circuit Court judge under section 16 of the Courts of Justice Act 1947. The judge asked whether Finn was lawfully detained when a breath specimen was required after a 27-minute interval at the station, and whether evidence obtained afterwards was admissible if the detention was unlawful.
Finn was arrested at 11.25pm on 9 June 2000 under road traffic legislation and taken to Dún Laoghaire Garda station, arriving at 11.40pm. Garda Darren Coogan observed him in an interview room from 11.44pm until 12.04am. The judgment records that the Garda said the observation was required by Garda guidelines to ensure Finn had not consumed food. A breath-test requirement was made at 12.07am; Finn refused at 12.08am and was charged in connection with that refusal.
Murray J said the Gardaí had a duty to make the statutory requirement with reasonable expedition. Whether ordinary delay was unreasonable depended on the circumstances. But he distinguished this case from one involving delay alone: the 20-minute wait was a prescribed minimum period of detention applied as a matter of practice for a forensic purpose.
The prosecution had to justify that procedure with objective reasons. Evidence that guidelines required the observation period did not establish that it was reasonably necessary to obtain proper or reliable breath samples. Murray J said such a justification could be supported by a competent witness, for example, evidence that the procedure followed equipment instructions or established practice.
The court answered the first question “No”: on the evidence before the Circuit Court, the prescribed detention period was not justified in law. It answered the second “Yes”, holding that the evidence obtained after that unjustified period was inadmissible. The ruling addressed the facts and evidence in this case stated; it did not decide that every 20-minute observation period is unlawful.