Expert Witness Services for Drug Driving Cases

Drug driving is a serious offence that can have profound legal and personal consequences for all involved. Since the introduction of Section 5A of the Road Traffic Act 1988 in 2015, legal limits for various drugs and medications have been strictly enforced. Whether illicit substances or prescribed medications are involved, exceeding these limits typically results in prosecution. Our expert witness services are designed to support solicitors and defendants by providing independent, scientifically informed evaluations that allow charges to be challenged when appropriate.

Understanding the Legal Framework

The S5A legislation governing drug driving categorises 17 substances into two groups:

1. Illegal Drugs
   Cocaine, Benzoylecgonine (cocaine metabolite), THC (cannabis), MDMA, LSD, Ketamine, Methylamphetamine, 6-MAM (heroin metabolite), Amphetamine

2. Medications
   Diazepam, Temazepam, Clonazepam, Flunitrazepam, Lorazepam, Oxazepam, Methadone, Morphine, Amphetamine*

*As amphetamine is also present in certain medications, its legal limit reflects therapeutic use despite also being a class B drug.

While illegal drugs are subject to ‘zero-tolerance limits’, thresholds for medications are higher, reflecting therapeutic use.

However, the ‘zero-tolerance limits’ are in fact not zero. They are very low levels in order to protect people who may have become passively exposed to the drug.

Even prescribed medications can lead to charges if the driver’s blood level exceeds the prescribed limit or if impairment is evident.

Key Defences in Drug Driving Cases

Post-driving consumption

A driver may assert that post-driving drug use caused their blood levels to exceed the legal limit. We can provide scientifically grounded opinions on whether such claims are plausible given the toxicology results and the defendant's account.

In charge but not driving

It is a defence to demonstrate that there was no likely prospect of driving while over the limit. This assessment involves complex analysis, particularly for drugs with highly variable elimination rates.

Unintentional consumption

If a defendant unknowingly consumed a substance, this may constitute a special reason to mitigate penalties. While precise calculations are not possible for drugs as they are for alcohol, expert insights can help establish whether the defendant’s explanation aligns with the evidence.

Prescription use

Drivers can defend themselves by proving that a medication was consumed according to medical instructions. However, if impairment is evident, this defence may not apply.

Services We Offer

We provide comprehensive expert witness services, including:

Review of Prosecution Data
We scrutinize the chain of custody and accuracy of the prosecution's analytical methods, ensuring the reported results meet legal and scientific standards.

Assessment of Procedural Integrity
Examination of procedural compliance in sample collection and testing is crucial. Any lapses can significantly impact the validity of evidence.

Special reasons cases
We interpret toxicology results along with the defendant's version of the events i.e. passive consumption, post-driving consumption or medications and evaluate whether their account fits with the toxicological data.

Expert Reports and Testimony
We produce clear, detailed reports suitable for court submission. They can also provide testimony to explain complex scientific concepts in an accessible manner.

Contact Us

For more information or to discuss your case, please contact us at contact@atxpert.co.uk. We are here to assist with all aspects of drug driving defences, offering expertise you can rely on when it matters most.