Drug Driving Defence
What is Drug Driving Defence?
Drug driving covers two distinct offences: driving while impaired by drugs, and driving with a specified controlled drug above a legal limit in blood. The second offence can catch drivers on prescribed medication even where they were not impaired.
The offence increasingly catches drivers on prescribed medication who had no reason to suspect they were breaking the law. Whether the drug was recreational or prescribed, the procedure used to obtain the blood specimen is the starting point for any defence.
Prescribed medication
A prescription is not an automatic defence.
Whether the medical defence applies depends on the prescription, the dose, and the advice you were given.
How a drug driving case proceeds
It begins with a roadside swab that screens for common drugs. A positive screen leads to arrest and a blood sample taken at the station by a healthcare professional. The sample goes to a laboratory, and results can take months, so you are often released to wait before any charge is brought.
These cases are heard at the Magistrates’ Court. The limits for illegal drugs are set very low, and the offence does not require proof that your driving was actually affected. A conviction brings a disqualification.
How the defence is built
A defence centres on the science and the procedure. How the blood sample was taken, stored, and transported all bear on whether the result can be relied on, and a sample that was mishandled can degrade before it is analysed.
Where the drug was lawfully prescribed and taken as directed, there is a defence open to drivers who were not actually impaired. Whether it applies depends on the medication, the dose, and the advice that was given.
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Common questions
- I was taking prescribed medication — is that still drug driving?
- It can be. The offence can catch drivers on prescription medicine, but there is a defence where the drug was prescribed and taken in line with the advice given, provided your driving was not impaired. Whether it applies depends on the medication and the dose.
- Can a blood test result be challenged?
- Yes. How the sample was taken, stored, and analysed all affect how much weight the result carries, and delay or poor handling can undermine it.
- Do the police have to prove I was impaired?
- For the limit-based offence, no. The prosecution only has to show the drug was in your blood above the set limit, not that your driving was affected. Impairment matters for a separate, older offence.
- How long do drugs stay in the system?
- Traces of some drugs, cannabis in particular, can remain in the blood for days after any effect has worn off, which is part of why these cases are contested.
Astons Law Chambers is authorised under the Bar Standards Board's Public Access scheme to accept instructions directly from members of the public. The practice is also authorised to conduct litigation, so the case can be run end-to-end without a separate solicitor. Suitability is assessed during the first call; where a solicitor is needed, Astons Law Chambers will say so and refer where useful.
For matters that qualify for public funding, see how legal aid works at Astons Law Chambers — eligible cases are referred to a partner solicitor firm at no cost.
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