The Government plans to make a new offence of drug driving under new legislation announced as part of the Queens speech.

Under the law as it stands it is an offence to drive whilst under the influence of drugs, whether illegal or legal. As part of this offence, the prosecution must prove not only the presence of drugs in the body but also that a persons driving was impaired as a result. This makes it a difficult offence to prove because often Courts cannot be sure that a person’s driving was impaired or that if it was impaired it was due to the presence of drugs.


The new proposal aims to introduce a new offence of “drug driving” similar to that of drink driving by introducing statutory limits to the amount of each substance a person can have in their system. It remains to be seen exactly what those limits will be and it will obviously depend on the substance concerned. There are obvious questions which arise from this. For example, exactly how will these limits be quantified? What level of cannabis will a person be able to have in their system without being prosecuted? Will the person accused of the new offence be prejudiced by residual amounts in their system from historical consumption of substances?

It is anticipated that the new drugalyser devices will be approved at some point next year. These devices will provide an indication as to whether a person may be over the prescribed limit for specific substances thereby giving police reasonable grounds for arrest in the event of a positive test. A blood or urine sample will still be required to be taken at the police station which will be intended to provide conclusive proof of the amount of drugs in a persons system.

It is important to remember that whilst the new offence has not yet been introduced, prosecutions for the current offence of driving whilst unfit through drugs (which will remain on the statute book) are still regularly brought.