Drug Driving Expert Witness

Bericon Forensics provides independent drug driving expert witness reports for criminal defence solicitors throughout England and Wales.

Our experienced forensic experts examine blood and urine results, prosecution toxicology evidence and accounts of drug use. We provide clear scientific opinions addressing the issues that matter in proceedings under sections 4 and 5A of the Road Traffic Act 1988. Our reports are prepared for use in the Magistrates’ Court and Crown Court and can be completed within urgent court timescales where possible.

Latest blog Drug Driving Overtakes Drink Driving

Our Drug Driving Expert Witness Services

Interpretation of Blood Drug Results

Our forensic toxicology experts interpret concentrations of controlled drugs and their metabolites in blood. We can explain what the result shows, what it does not show and how it should be interpreted within the circumstances of the case.

A defendant may provide information about the amount of a drug used, the time of use and the method of administration. Our drug driving expert witnesses can assess whether that account is scientifically consistent with the analytical findings.

Where appropriate, we can consider whether:

• the stated use could reasonably have produced the reported result;
• the result suggests more recent or additional consumption;
• post-driving consumption may have contributed to the result;
• or the concentration is inconsistent with the account provided.

Any limitations in the available scientific evidence will be clearly explained.

Review of Prosecution Toxicology Evidence

Our forensic experts can review the prosecution laboratory report and supporting case papers.

This may include consideration of:

• the analytical findings;
• the drugs and metabolites reported;
• measurement uncertainty or deductions applied to the result;
• sample collection and continuity;
• storage and stability issues;
• the interpretation given by the prosecution;
• and whether the conclusions are properly supported by the evidence.

Where necessary, we can advise whether additional laboratory documentation or unused material should be requested.

Section 5A Drug Driving Cases

Section 5A of the Road Traffic Act 1988 concerns driving, attempting to drive or being in charge of a vehicle with a specified controlled drug above the prescribed limit.

In these cases, the prosecution generally relies on the concentration measured in a blood sample. It is not normally required to prove that the driver showed visible impairment. A forensic expert may still be required to assess the reliability and interpretation of the analytical result, the timing of consumption, prescribed use or another scientific issue raised by the defence.

Section 4 Unfit Through Drugs Cases

Section 4 cases concern whether a person was unfit to drive through drink or drugs.

These cases may involve observations of driving, police evidence, field impairment tests, medical examinations and toxicology results. A forensic drug expert can consider whether the detected substance and reported concentration could have contributed to impairment. The evidence must be assessed as a whole because the presence of a drug does not automatically establish the extent of any impairment.

Medical and Prescription Drug Driving Cases

The prescribed limits include several medicines that may be lawfully supplied for medical treatment. A statutory medical defence may be relevant where a specified controlled drug was prescribed or supplied for medical or dental purposes and was taken in accordance with the directions provided.

Our drug driving experts can examine:

• prescription records;
• dosage instructions;
• the defendant’s pattern of medication use;
• the reported blood concentration;
• and whether the scientific findings are consistent with therapeutic use.

The availability of any legal defence is a matter for the court. Our role is to provide an independent scientific opinion on the toxicology evidence.

What Information Does a Drug Driving Expert Need?

To provide an initial opinion or quotation, we may require:

• the prosecution laboratory report;
• the witness statements;
• the MGDD forms or equivalent procedure documents;
• the time of driving and blood sampling;
• the defendant’s account of drug or medication use;
• prescription or medical records where relevant;
• and the prosecution case summary.

We can advise at an early stage whether a full expert witness report is likely to assist.

Drug Driving Expert Reports for Solicitors

Bericon Forensics works primarily with criminal defence solicitors and barristers.

Our reports are:

• independent and evidence based;
• written in clear, accessible language;
• focused on the questions raised by the defence;
• prepared in accordance with the applicable court requirements;
• suitable for privately funded and Legal Aid Agency cases;
• and supported by expert court attendance where required.

We understand the pressures created by court directions, funding requirements and late service of prosecution evidence. Our team aims to provide responsive assistance from initial instruction through to the witness box.

Frequently Asked Questions

What does a drug driving expert witness do?

A drug driving expert witness examines scientific evidence in a criminal case and provides an independent opinion for the court. This may include interpreting blood drug results, reviewing laboratory evidence and assessing whether an account of drug use is consistent with the findings.

Can a drug driving blood result be challenged?

A result can be reviewed to determine whether the analysis, reporting and interpretation are scientifically reliable. The fact that a result exceeds a legal limit does not prevent a forensic expert from examining how the sample was obtained, analysed and interpreted.

Can an expert calculate the drug level at the time of driving?

It is sometimes possible to discuss whether a concentration may have been higher or lower at an earlier time. However, precise back-calculation is often unreliable for drugs because absorption and elimination vary considerably between individuals. Any scientifically valid conclusions and limitations will be explained in the report.

Does a positive drug result prove impairment?

A positive result proves that the laboratory detected the reported substance, subject to the reliability of the analysis. It does not necessarily establish the exact degree of impairment.

For section 5A cases, the central issue is usually whether the concentration exceeded the prescribed limit. For section 4 cases, the court considers whether the person was unfit to drive.

Can you assess cannabis and THC results?

Yes. Our forensic experts regularly examine THC, carboxy-THC and other cannabinoid findings. We can consider the concentration, reported time of use, sampling time, pattern of cannabis use and whether the account is consistent with the result.

Can you assess cocaine and benzoylecgonine results?

Yes. We can interpret cocaine and benzoylecgonine concentrations and consider the possible timing and pattern of use. The relationship between the parent drug and its metabolites may provide useful information, although conclusions depend on the circumstances and available evidence.

Do you accept Legal Aid Agency instructions?

Yes. We regularly work with criminal defence solicitors in legally aided cases and can provide quotations suitable for prior-authority applications