Supreme Court Overturns High Court Ruling on Drink-Driving Blood Sample Custody

The Supreme Court has unanimously overturned a High Court ruling that had cast doubt on hundreds of drink-driving prosecutions. The Director of Public Prosecutions (DPP) appealed the July 2023 High Court decision by Judge Sara Phelan, which quashed a man’s drink-driving conviction due to issues with the chain of custody for his blood sample.

This High Court ruling had put prosecutions nationwide on hold, affecting a large number of cases annually, as courts deal with up to 7,000 drink-driving prosecutions based on blood or urine specimens. The High Court had ruled that a break in the chain of custody for a blood specimen, taken on August 21st, 2022, entitled the man to have his conviction and two-year driving ban overturned.

The specimen, containing 126ml of alcohol per 100ml of blood (more than twice the legal limit of 50ml), was taken by a doctor, sealed in containers, and handed to a garda. The District Court had relied on statutory presumptions from the Road Traffic Acts, stating that completed certificates regarding the sample were proof of facts unless proven otherwise. However, the High Court ruled these presumptions did not cover the chain of custody after sealing, requiring the prosecution to provide evidence of storage to exclude interference.

In her Supreme Court judgment, Judge Iseult O’Malley stated that the analysis certificate, not the specimen itself, serves as evidence. She clarified there is no general legal rule requiring proof of a chain of custody for real evidence, and a failure to prove it does not render the analysis certificate inadmissible. The Act considers completed forms sufficient evidence unless proven otherwise, and the prosecution is not required to exclude every hypothetical possibility. The Supreme Court found the High Court erred in its interpretation.