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Drug driving defences

Medical defence

There are a number of controlled drugs which are used in medicine and which if taken could impair driving ability such as:

Cannabis (THC)

There are limited grounds for medical defence if a motorist is caught driving with these substances in their system if their driving was severely impaired. However, there is a medical defence available for people taking controlled drugs for medical reasons if their driving was not impaired. A medical defence for drug driving can be used as long as:

  • The drugs were prescribed, supplied, or sold to treat a valid medical or dental problem and…
  • The drug was taken correctly following directions of a medical professional or in accordance with the information from the drugs manufacturer.

Spiked drug driving defence

It may be possible to mount a defence for a drug driving charge if you took controlled drugs without your knowledge by being spiked or laced. In order to take this line of defence a defendant would need to prove:

  • That they would have been fit to drive and below any drink or drug drive limit if they had not been spiked or laced.
  • They had no knowledge that they were spiked or believed their ability to drive was impaired.

It will be decided by a court if the defendant is to receive any penalty for an offence if they take the spiked defence.


It is possible for a defendant to resist a drug drive charge by claiming emergency circumstances. Their ability to do so would depend on:

  • The circumstances of the emergency
  • Whether there were alternative transport options
  • The distance that was driven

If you have been charged with a drug driving offence under any circumstances and would like to discuss your defence options contact us and one of our expert motoring solicitors for the best legal advice and guidance.