Law question for solicitor or student

Remember folks that convictions are rarely secured on a single piece of evidence. The idea is to prove beyond reasonable doubt that a person is guilty.

A urine test alone, would not be sufficient. As has been pointed out above, cannabis, among other drugs, could be present in urine for many weeks after having consumed it. A positive urine sample alone would not prove, beyond reasonable doubt, that a person "is under the influence of intoxicating liquor or a drug to such an extent as to be incapable of having proper control of the vehicle".

However, a statement from the Garda as to his observation of the defendant's driving and his behaviour at the roadside, coupled with the evidence that the defendant's urine tested positive for cannabis, could very easily serve as sufficient evidence that the person was "under the influence of intoxicating liquor or a drug to such an extent as to be incapable of having proper control of the vehicle".

All the evidence in the world which said that you hadn't enough cannabis in your system to impair your driving wouldn't be enough. The Garda was of the belief that you were intoxicated, and you tested positive for cannabis.