Ali v Director of Public Prosecutions

An evidential breath-machine reading is presumed reliable, but the presumption is rebuttable. The defendant bears only an evidential burden of adducing relevant evidence capable of raising a challenge. Once that burden is discharged, the prosecution must prove, beyond reasonable doubt, that the reading remains reliable.

The ultimate issue is factual. A court may reject unchallenged expert evidence where there is a rational evidential basis for doing so. A defendant’s assertion that insufficient alcohol was consumed does not, without more, require the court to reject the reading. An error concerning the burden of proof is immaterial where the court independently finds, to the criminal standard, that the machine was operating correctly.

The appellant was convicted by a Deputy District Judge at Westminster Magistrates’ Court of driving with excess alcohol, contrary to Road Traffic Act 1988, section 5(1). An evidential breath machine recorded 46 micrograms of alcohol in 100 millilitres of breath, against a prescribed limit of 35 micrograms.

The appellant relied on expert evidence concerning calibration and on his account of alcohol consumption and reflux. The Deputy District Judge treated the burden of rebutting the machine’s presumed reliability as resting on the appellant on the balance of probabilities, but also found beyond reasonable doubt that the machine was working correctly. The appeal by way of Case Stated concerned the burden and standard of proof, the treatment of the expert evidence, and whether the conviction could stand.

1. The appeal was dismissed. The Deputy District Judge answered all four stated questions affirmatively and was entitled to convict.
2. There are two relevant presumptions or assumptions. The common law presumption of regularity means that an evidential breath machine is presumed to be in good working order and its reading reliable. Separately, Road Traffic Act 1988, section 10(2), provides a statutory assumption concerning the alcohol level at the time of the alleged offence.
3. The defendant has an evidential burden only. The defendant may adduce relevant evidence which, if accepted, provides material from which a reasonable inference of unreliability may be drawn. Once relevant evidence is adduced, the prosecution must prove beyond reasonable doubt that the reading is reliable notwithstanding that evidence. The Deputy District Judge therefore erred in treating the appellant as bearing a legal burden on the balance of probabilities.
4. That error did not affect the result. Reliability was ultimately a factual assessment. The judge was entitled to reject the expert evidence because it was based on a general and dated quality-framework document, without examination of the particular machine or its calibration records, and was contradicted by direct evidence that the machine was within its calibration period.
5. The judge was also entitled to reject the appellant’s evidence and to take account of the failed roadside tests, the smell of alcohol, glazed eyes, the operator’s evidence, the absence of error messages and the machine’s self-calibration feature. These matters provided a rational basis for finding the reading reliable.
6. The words “on balance” in the lower court’s reasoning were infelicitous, but the judgment had to be read as a whole. Its concluding findings showed that the judge was satisfied beyond reasonable doubt that the machine was reliable and that the offence was proved.

• Westminster Magistrates’ Court: the Deputy District Judge convicted the appellant on summary conviction of driving with excess alcohol.
• High Court (Administrative Court): on an appeal by way of Case Stated, the court dismissed the appeal and upheld the conviction.