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What does the law say about illegal drugs?

Any trace of illegal drugs in your system whilst driving can lead to a drug driving accusation. This can create difficult matters as drugs often stay in the body for several days after use.

‘Accidental exposure’ is like passive smoking, whereby smokable drugs such as cannabis, can enter the system due accidentally. If you are the driver of a vehicle and the passenger is smoking cannabis, this could cause you to exceed the legal level of cannabis in your system. The legal limits for drug driving are set just above zero to account for this. 
The legal cut-off levels for illegal drugs are as follows:

  • Cocaine (or Benzoylecgonine) – 10 micrograms per litre
  • Cannabis – 2 micrograms per litre
  • LSD – 1 micrograms per litre
  • Ketamine – 20 micrograms per litre
  • MDMA, ecstasy and crystal meth – 10 micrograms per litre
  • Heroin – 5 micrograms per litre
prescription drug driving
drug driving penalties

There will also be aggravating/mitigating factors that may affect the seriousness of the case. Aggravating factors that affect drug driving may include:

  • Previous convictions regarding the relevant offence
  • Location of the offence
  • Passengers in the vehicle when the offence took place
  • Levels of traffic or pedestrians in the area

Mitigating factors may include:


  • No previous convictions
  • Genuine emergency involvement
  • A shorter length of journey
  • Age – a lack of maturity may affect the responsibility of the offender
  • Remorse