This is another area of law that is changing weekly. It used to be that the court had to be satisfied that you had some sort of drug in your system and that the police could demonstrate beyond doubt that it had impaired your driving in some way. Now, there are tests the police will employ that can detect a number of different substances and there are fixed limits. As with the drink driving laws - if you are over those limits they can prosecute you and you are likely to face a mandatory ban - even if they cannot show you were "impaired" by that substance. It is a new area of law and we have dealt with many of these cases and can provide you expert advice on the likely outcome and whether you can challenge the case.