Background
On 1 February 2025, Jack Ambrose was stopped by police while driving in Chester at 00:30 am. A roadside breath test showed 41 microgrammes per 100 millilitres of breath (the legal limit is 35 µg). He told the officer he had consumed one glass of red wine more than 20 minutes earlier. Further breath specimens taken at the police station showed readings of 42 and 43 µg. Ambrose was charged with driving over the prescribed limit under section 5(1)(a) of the Road Traffic Act 1988.
On 18 February 2025, Ambrose pleaded guilty but claimed his drink had been spiked with tequila without his knowledge by Ella Stewart, who was with him that evening. A forensic scientist’s report, agreed by the prosecution, concluded that without the spiking, his breath reading would have been approximately 36 µg—below the legal limit. On 30 September 2025, Deputy District Judge Munir held a hearing to determine whether “special reasons” existed under section 34(1) of the Road Traffic Offenders Act 1988 that would justify avoiding the mandatory 12-month driving disqualification. The judge found the spiking had occurred without Ambrose’s knowledge but rejected the special reasons claim, disqualifying him for 36 months.
The Court’s Holding
The High Court allowed Ambrose’s judicial review, finding the judge had erred in law. The judge had incorrectly applied Delaroy-Hall v Tadman (which involved blood tests) and failed to apply the more recent and directly relevant authority of R v Wong. In Wong, the Divisional Court held that special reasons could be established where (i) the defendant was unaware alcohol had been ingested, (ii) the resulting reading was only just above the prosecution threshold, and (iii) without the ingested substance the reading would have fallen below that threshold. These facts were indistinguishable from Ambrose’s case: his reading of 42 µg was only just above the 40 µg prosecution threshold (a practice established in Home Office Circular 46/1983), and his reading would have been 36 µg without the tequila.
The court held that Delaroy-Hall was distinguishable because it predated the breathalyser regime and the 40 µg prosecution threshold, involved blood testing (not breath), and did not concern spiked drinks. The court clarified that while Pugsley requires showing the excess over the statutory maximum is attributable to spiking, Wong properly extended this principle to the breath-testing context: the relevant inquiry is whether the excess over the prosecution threshold is attributable to the spiking. Because the judge failed to find the facts capable in law of amounting to special reasons, his decision was reversed.
Rather than substituting its own judgment, the court remitted the case to a freshly constituted magistrate bench to determine whether special reasons should be found, applying the correct legal test and based on the preserved factual findings that Ambrose’s drink was spiked without his knowledge and that his reading would have been 36 µg without it.
Key Takeaways
- Spiked drinks can constitute special reasons for avoiding mandatory driving disqualification in drink-driving cases.
- In breath-testing cases, courts should ask whether the excess over the 40 µg prosecution threshold is attributable to the spiking, not whether the excess over the statutory 35 µg limit is attributable to it.
- R v Wong is the controlling authority for spiked-drink cases in the breath-testing context; Delaroy-Hall v Tadman (a blood-testing case) should not be applied to prevent special reasons findings.
- Special reasons findings remain matters of judicial discretion even when the legal requirements are satisfied; courts retain discretion on whether to impose disqualification at all or for a reduced period.
Why It Matters
This decision clarifies the law governing defences based on unknowing consumption of alcohol through drink-spiking in drink-driving prosecutions. By anchoring the test to the prosecution’s own 40 µg practice threshold rather than the statutory 35 µg limit, the court aligned the special reasons doctrine with fairness principles: a driver who would not have been prosecuted but for circumstances beyond his control may now seek to avoid mandatory disqualification. The decision resolves a conflict between two precedents and establishes that modern breath-testing jurisprudence, not outdated blood-testing principles, governs this issue.
For defendants facing drink-driving charges where alcohol was consumed unknowingly or without opportunity to decline, this decision reopens the possibility of avoiding mandatory disqualification—a significant outcome given that such disqualifications cause substantial practical hardship to innocent drivers whose impairment fell marginally above the prosecution threshold solely because of the spiking.