TORONTO - Trying to beat a drunk-driving conviction by asking for certain records related to the breathalyzer used has become more difficult following a ruling Wednesday by Ontario's top court.

The ruling limits disclosure of records accused frequently ask for in drunk-driving prosecutions.

"It is critical for the efficient operation of trial courts, especially those in which alcohol-driving offences occupy a prominent place on the docket, that they be able to control their process," the Appeal Court said.

"This includes the authority to discourage unmeritorious third-party records applications that devour limited resources."

The case arose when Ottawa police pulled over David Jackson for erratic driving and he failed a breath test. They charged him with drunk driving.

Before his Ontario court trial, Jackson asked Judge Jack Nadelle to order police to turn over records related to the history and performance of the device that measured his blood alcohol concentration. Nadelle did so in August 2013 on the basis they were relevant to the defence, prompting the police service and prosecution to appeal.

In April last year, Justice John Johnston of the Superior Court of Justice upheld the disclosure order, sparking the further appeal.

"The issues raised here emerge in a thoroughly unremarkable alcohol-driving prosecution," Appeal Court Justice David Watt said in the unanimous decision. "About as routine as it gets."

And even though the requested documents had been turned over, the higher court agreed to hear the case to help settle conflicting case law.

In ruling against Jackson's request, the Appeal Court noted he was given material that is routinely turned over in such cases, including records of the tests and checks executed by the Intoxilyzer 8000C to ensure it was working properly. Any failure precludes the machine from taking a breath sample.

Jackson wanted more but the Appeal Court said nothing in the records he did get showed any problem with the device or error by the technician that might have made the additional materials relevant. Suggestions to the contrary were speculative, and the historical data sought would prove nothing about the credibility of the officers involved in his case.

"A fishing expedition," Watt called it. "Season closed."

In a post-script to the lengthy decision, the court offered guidance to judges trying to decide if a record is relevant to the issue of whether an approved breathalyzer was either malfunctioning or operated improperly and therefore should be turned over to the accused.

For example, the court said the fact that a record exists showing the device may not have worked properly in the past is not enough on its own to make it relevant. Nor is any previous record related to the credibility of the operator of the instrument.

News from © The Canadian Press, 2015