The High Court ruled that prosecutors do not have to give positive evidence of a roadside breath-screening device’s calibration when establishing that a Garda formed a reasonable, bona fide opinion to justify an arrest.
In a judgment delivered on 6 February 2020, Ms Justice Hyland answered “No” to a question referred by Cavan District Court Judge Denis McLoughlin under section 52 of the Courts (Supplemental Provisions) Act 1961. The question arose during the hearing of a case against Kian McGuigan, who had pleaded not guilty to a charge alleging that he drove with an excess concentration of alcohol in his urine. Two other charges arising from the same events were outside the case stated.
The District Court judge found that no evidence had been given about the calibration of the Dräger Alcotest 6510 used in a roadside breath test. The device has different fail thresholds for specified drivers and other drivers. He also found that the failed test materially contributed to Garda Michael O’Shaughnessy’s opinion and that the Garda would not necessarily have made the arrest without it.
Justice Hyland upheld those factual findings. She noted that the defence had not asked the Garda about the device’s calibration, and there was no evidence before the trial judge identifying a reason to question whether the fail result applied to McGuigan.
The judge said the calibration level was relevant: if the Garda relied on a failed test, he had to be sure the driver had failed. But the prosecution did not have to exclude every possible factual situation that could invalidate the opinion. Where evidence showed that the Garda formed a reasonably held, bona fide opinion, and that evidence had not been undermined by the defence, it was sufficient to establish the opinion at this stage.
Justice Hyland said the ruling did not require the court to assume that the device had been correctly calibrated. The defence could raise calibration in cross-examination; evidence that the device was set to the wrong level, or that the Garda did not know its setting, could undermine the basis for the opinion.
The High Court answered the referred question in the negative. The judgment determined the legal issue referred by the District Court; it did not decide the underlying charges against McGuigan.