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Facing a drug driving charge can be confusing and stressful. The law in Scotland distinguishes between several different offences under the Road Traffic Act 1988, each dealing with a different aspect of drug-related driving. This page explains, in plain terms, how the legislation works — and what to expect if you are investigated or charged.
We cover the key sections that apply to drug driving:
Each of these offences carries serious consequences — including disqualification, fines, and potential imprisonment.
At Scottish Driving Law, our solicitors specialise in road traffic defence and regularly represent clients throughout Scotland in drug driving cases. We can help you understand the charges, assess the strength of the evidence, and prepare the best possible defence.
Driving while unfit means driving, attempting to drive, or being in charge of a motor vehicle when your ability to drive properly is impaired because of alcohol or drugs.
This is covered by Section 4 of the Road Traffic Act 1988, which applies throughout Scotland.
Unlike the “drug driving” offence under Section 5A (which is based on specific drug limits in the blood), Section 4 focuses on impairment — whether your ability to drive safely has been affected by drink or drugs, regardless of the amount consumed.
Section 4(1) provides that:
“A person who, when driving or attempting to drive a mechanically propelled vehicle on a road or other public place, is unfit to drive through drink or drugs is guilty of an offence.”
Section 4(2) applies to being in charge of a vehicle while unfit through drink or drugs.
A person is considered unfit to drive if their ability to operate a vehicle is impaired to any extent due to alcohol, illegal drugs, or certain medications.
This could include:
If the police suspect impairment, they may:
A conviction under Section 4 carries:
Possible defences include:
Early legal advice is essential.
Drug driving refers to driving, attempting to drive, or being in charge of a motor vehicle while certain controlled drugs are present in your system above specified legal limits.
Introduced in Scotland to strengthen drug driving enforcement, Section 5A of the Road Traffic Act 1988 makes it an offence even if your driving is not visibly impaired.
It is an offence if:
“A person drives or attempts to drive (or is in charge of) a motor vehicle on a road or other public place after having taken a specified controlled drug, and the proportion of that drug in their blood or urine exceeds the specified limit.”
The law sets specific limits for 17 controlled drugs, including:
The limits are very low — designed to rule out accidental exposure rather than impairment.
A defence may apply if:
Police can require a roadside drug test (saliva swab) if they suspect drug use or an offence.
A positive test usually leads to arrest and a blood test at the station to confirm drug levels.
Penalties
If convicted under Section 5A:
Section 6 gives police authority to require a driver to provide a preliminary test for alcohol or drugs.
A test may be required if police:
It is an offence under Section 6(6) to refuse or fail to provide a preliminary test without reasonable excuse.
Refusal can lead to arrest and further testing at the police station.
Once at the police station, Section 7 governs the taking of evidential specimens for analysis — such as breath, blood, or urine.
Police Powers
An officer may require a person to provide:
These are analysed to determine drug or alcohol levels. In drug cases, a blood sample is usually taken.
Under Section 7(6), it is an offence to fail, without reasonable excuse, to provide a specimen when required.
This is known as “failing to provide” and is treated as seriously as drug driving itself.
Valid reasons may include:
Nervousness or embarrassment are not reasonable excuses.
Section 4 – Driving while unfit through drink or drugs (impairment-based)
Together, these provisions form the legal framework for detecting and prosecuting drug driving in Scotland.
Section 4 is an “impairment” offence. This means you are charged because the police believe your ability to drive properly is impaired by drugs , regardless of the specific amount in your system. Section 5A is a “specified limit” offence. This makes it illegal to be over the legal limit for a specific controlled drug in your blood or urine, even if your driving does not appear to be impaired.
Can I be charged for driving on my prescription medication?
Yes. The list of 17 controlled drugs under Section 5A includes common prescription drugs like diazepam, methadone, and morphine. However, you may have a legal defence if the drug was prescribed for a medical purpose and you followed all the advice given by your doctor or pharmacist.
The penalties are severe for both Section 4 and Section 5A offences. A conviction will result in:
Refusing to provide an evidential specimen (like blood or urine) at the station without a “reasonable excuse” is a serious offence under Section 7(6) of the Road Traffic Act 1988. This offence is treated as seriously as drug driving itself and carries the same penalties, including a minimum 12-month ban, an unlimited fine, and potential imprisonment .
No. The law is clear that nervousness or embarrassment do not count as a “reasonable excuse”. A valid reasonable excuse would typically be a genuine medical condition that physically prevents you from providing the required sample.
At Scottish Driving Law, we regularly represent clients accused of drug driving, failing to provide a specimen, and related offences under the Road Traffic Act 1988.
We can:
If you are facing any drug driving allegation, contact us today for expert, confidential advice and skilled representation.
If you have been arrested, charged, or invited for interview in connection with a drug driving allegation, contact Scottish Driving Law today. Our experienced road traffic solicitors are available to provide clear, practical advice and robust representation at every stage of your case. We act for clients across Scotland and can assist you immediately.
Last reviewed for accuracy on 30 October 2025, by Joseph MacPherson, Scottish Driving Law, a solicitor enrolled with the Law Society of Scotland.
Thank you so much for the quick, clear and decisive advice regarding my alleged speeding fine. Obviously you know the law in depth in this area. My mind is now at rest following our conversation and the future is a little less stressful as a result.
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