Director of Public Prosecutions v Bolton

Under section 15 of the Road Traffic Offenders Act 1988, a defendant relying on post-driving alcohol must prove both that alcohol was consumed after driving and that, without it, the prescribed limit would not have been exceeded. A defendant may establish this without expert evidence only where the facts are obvious and a lay tribunal can reach a reliable conclusion. Where the issue depends on scientific matters that are not obvious, medical or other scientific evidence is required. Magistrates must assess the defendant’s account against the relevant scientific background rather than accept it in isolation.

The Director of Public Prosecutions appealed by way of case stated from a decision of Telford Magistrates’ Court. The defendant had been charged under section 5(1)(a) of the Road Traffic Act 1988 after providing a blood specimen showing 155 milligrams of alcohol per 100 millilitres. He relied on alcohol consumed after driving and contended that his earlier consumption had not placed him over the prescribed limit.

The magistrates accepted his account, considered the issue obvious, and found that medical evidence was unnecessary. The central issue was whether they had been entitled to reach that conclusion without scientific evidence.

1. Appeal and statutory burden. The appeal was allowed. Section 15 of the Road Traffic Offenders Act 1988 creates an assumption that the proportion of alcohol at the time of the alleged offence was at least that shown by the specimen. The defendant bears the burden of proving both post-driving consumption and that, without it, the prescribed limit would not have been exceeded.
2. Need for scientific evidence. The guidance in Pugsley v Hunter [1973] RTR 284, as adopted and qualified in Dawson v Lunn [1986] RTR 234, applies. Lay magistrates may decide an obvious case without expert assistance. Where the relationship between the alcohol consumed, the specimen reading and the prescribed limit cannot be assessed reliably by lay reasoning, the defendant must call medical or other scientific evidence.
3. Error by the magistrates. The magistrates had accepted the defendant’s evidence without testing it against the scientific evidence needed to explain how a reading of 155 had been reached. They therefore fell into error in treating the case as obvious and concluding that further evidence was unnecessary. Patterson v Charlton [1986] RTR 18 confirmed that the evidential burden rested on the defendant. The discussion in R v Andrew Drummond [2002] 2 Cr App R 25 supported the relevance of matters such as alcohol consumed after driving, blood-breath ratio, elimination rate and body weight.
4. Order. The case was remitted to Telford Magistrates’ Court. The defendant was to have an opportunity to reopen his case and call further medical or scientific evidence. If he did not do so, the magistrates were directed to convict for driving with excess alcohol.

• High Court (Administrative Court): On an appeal by way of case stated, the magistrates’ decision was set aside and the case was remitted to Telford Magistrates’ Court with directions.
• Telford Magistrates’ Court: The defendant was acquitted after the magistrates accepted his post-driving alcohol defence without requiring scientific evidence.