A Kerry judge has thrown out two separate drink-driving cases because of the danger the defendants inhaled alcohol from their own urine while in garda custody.

The rulings, by Judge James O'Connor, came as there was increasing concern at government level over the high number of non-convictions in drink-driving cases.

The biggest anti-drink driving campaign in the history of the State got under way last week in a bid to reduce the number of road deaths over Christmas.

Morale among gardai charged with enforcing the drink-driving laws has been affected by, what they regard as, the use of "loophole law" by defending solicitors, which means securing convictions in Section 49 (drink-driving) cases has become a minefield for prosecuting officers.

Last month, at Killorglin District Court, two separate drink-driving cases were dismissed after the presiding judge ruled that the steam of the defendants' urine could have affected their alcohol readings taken during subsequent breath testing.

They were not the first cases where Judge O'Connor has agreed with defence submissions that inhalation of urine fumes could have skewed breath-test results and cases should be dismissed. The law covering Section 49 requires that a person suspected of drink driving must be observed by a garda for 20 minutes at a garda station before their breath sample is taken.

During that 20-minute period they must not consume anything by mouth.

In both cases, the solicitor, Mr O'Connell, argued that during this 20-minute period both his clients had used a toilet to urinate. Because the two men urinated with their backs to the prosecuting garda, the 20-minute observation period had been interrupted. The solicitor argued that a new 20-minute observation period should have begun when his clients returned from the toilet and that the cases should be dismissed.

Judge O'Connor agreed. He stated that the purpose of the 20-minute observation period is to ensure nothing is taken by mouth that may affect the reading from the breath test.

"Nil by mouth is the same as nil by nose," Judge O'Connor declared. "When he is urinating, he is inhaling vapourised alcohol and there's always steam off it."

Assistant Garda Commissioner Eddie Rock, who is in charge of the Garda Traffic Corps, said yesterday that the two cases which were dismissed in Killorglin served to highlight the difficulties faced by gardai in successfully prosecuting cases of alleged drink driving.

"I don't think it is appropriate for me to say anymore about it at this stage," he said.

A Department of Justice spokesman confirmed that the gardai are currently examining the implications of the outcomes in the cases.

The low level of convictions in drink-driving cases and the large number of drink-drive cases which have still not come before the courts, despite dating back to 2003, has led to questions in the Dail. More than 71,000 drivers have faced drink-driving charges in the last five years but fewer than 39,000 -- just over 50 per cent -- were convicted.

Last week, the Sunday Independent revealed that nearly 10,000 suspected drunk drivers arrested by gardai between 2003 and 2007 have still not had their cases heard.