Michael Ryan, aged 20, of Ballyshoneen, Berrings, Co Cork, who described himself as a student and senior rugby player, admitted when he was stopped by gardaí that he had smoked two cannabis joints.

However, at Cork District Court yesterday, he pleaded not guilty to driving a car while being under the influence of an intoxicant, to such an extent that he was incapable of having proper control of the car.

Unlike alcohol, where the Road Traffic Act sets out exact levels of alcohol in blood or urine to show that an offence has been committed, the level of cannabis in a motorist’s system is not established by analysis. Only the presence or absence of cannabis in the blood or urine is established.

Judge Olann Kelleher said the fact that the motorist had smoked cannabis was not enough in itself to make out the case for the prosecution on being incapable of having control of the car.

Garda Kieran Crowley testified that he saw the car “weaving” on the road and when he later spoke to the motorist he got a strong smell of cannabis from the car and from the driver.

Mr Ryan told his barrister, Stephen O’Donoghue, yesterday at Cork District Court: “I did not weave or cross over or anything like that.”

Cross-examined by Insp Gary McPolin, he said he had been smoking cannabis regularly at that time and felt capable of driving after two joints. He said he smoked them in a friend’s house and not in the car.

“Garda Crowley said you were slightly weaving,” the inspector said. Mr Ryan replied: “I am 100% sure I was not weaving.”

The inspector said: “You drove within half an hour of smoking two cannabis joints, you knew you were running the gauntlet.”

Mr Ryan replied: “I thought I was capable.”

The inspector said: “It was a good day for Ireland you were stopped that night.”

Garda Brian White observed the car that night and he thought that, for a light drizzle, the car wipers were on full at 10.30pm that night, Dec 27, 2012.

Dismissing the case, Judge Kelleher said it was foolhardy to have driven after smoking cannabis. But he said: “It is unusual that the only complaint by Garda White was the wipers. I will give him the benefit of the doubt. I dismiss the case.”

The judge added: “He should not have been driving but I do not find he was unfit to drive, on the evidence.”

Earlier in the hearing, Judge Kelleher said that the fact that Mr Ryan had smoked cannabis was not enough in itself to make out the case for the prosecution on being incapable of having control of the car.