Evidential requirements in drink driving and drug driving prosecutions: chain of custody
- muirisgavin
- Dec 4, 2025
- 2 min read
The High Court decision in Andrejs Ratinskis v DPP clarified key evidential requirements in drink driving prosecutions, especially the chain of custody for blood and urine samples.
Facts of the case: In 2022, Ratinskis was stopped at a Mandatory Intoxicant Checkpoint in Newbridge and arrested under s.10(7) of the Road Traffic Act 2010. He provided a blood sample to a designated doctor at Newbridge Garda Station. The doctor used a kit supplied by the Medical Bureau of Road Safety (MBRS), which includes two glass bottles, seals, and a form (the “s.15 certificate”). The sample was split into two sealed bottles. One was given to Ratinskis; the other, along with the completed form, was sealed in a box and sent to MBRS for analysis.
MBRS issued a certificate (the “s.17 certificate”) showing 126mg of alcohol per 100ml of blood—well above the legal limit of 50mg under s.4(2)(a) RTA 2010. Ratinskis was prosecuted for driving with excess alcohol. However, the Garda’s evidence did not explain where the sample was kept between collection and posting.
At trial, the Defence argued the chain of custody was incomplete and sought a dismissal. The District Court refused. Ratinskis then obtained leave for judicial review.
The High Court held that statutory presumptions under section 15(4), section 17(4), and section 20(2) of the Road Traffic Act 2010 do not cover the integrity of the sample during storage. Certificate evidence cannot fill this gap. Therefore, the conviction was quashed.
Statutory Presumptions:
Section 15(4): Presumes compliance with subsections (1)-(3) until proven otherwise.
Section 17(4): Similar presumption for analysis procedures.
Section 20(2): A completed certificate is sufficient evidence of the facts stated and compliance by the doctor or nurse—until the contrary is shown.
These presumptions simplify prosecutions by allowing certificate evidence without calling witnesses. However, they do not eliminate the need to prove chain of custody.
Ms. Justice Phelan ruled: Presumptions cannot replace proof of custody, the State must lead evidence showing where and how the sample was stored before posting and Judicial Review was appropriate because an appeal would allow the prosecution to “mend its hand.”
Ms. Justice Phelan noted that any inconsistency between the law and its practical application is for the Oireachtas to address.
The broad impact of this Decision: Many drink driving and drug driving prosecutions now require explicit chain-of-custody evidence. Due to this, many District Court prosecutions are being adjourned pending clarification around whether the State will appeal this Decision.
About the author: Sinéad Leahy is a Trainee Solicitor with Dermot G. O'Donovan Solicitors. Contactable on leahys@dgod.ie
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