Reforming the Hair Strand Testing Industry - Why Expert Interpretation Matters (21 May 2025)

For years, the family court system has relied heavily on simplified drug and alcohol test results. However, recent High Court and Court of Appeal rulings confirm that hair strand tests should be considered expert opinion evidence—not just laboratory results.

In D, Re (Children: Interim Care Order: Hair Strand Testing) [2024] EWCA Civ 498, Mr Justice Cobb concluded that Her Honour Judge Jacklin KC was wrong to attach “such presumptive weight” to the hair strand test results and that she did not consider sufficiently "the context of the broader picture" of evidence.

One of the grounds of the mother’s appeal in this case was that the judge had formed erroneous conclusions about the hair strand testing results, wrongly treating the general opinion on the first laboratory as to its findings. Mr Justice Cobb agreed, and allowed the appeal. He said that the judge had been wrong to attach such weight to the results of the hair strand tests.

In the circumstances, Mr Justice Cobb gave the following guidance for advocates in cases involving hair strand testing:

1. Draw the judge’s attention to what science can and cannot tell you.
2. Carefully examine the hair strand test reports in full; as far as it is thought helpful or appropriate to do so, they should distil their contents accurately so as to provide with Judge with a reliable summary, not just rehearsal or précis of the general ‘Summary’ or ‘Opinion’ section,
3. Assist the Judge to consider the hair strand test results in the context of the whole of the evidence, including:
   a) The statements of those who are alleged to have exposed the children to the drugs identified;
   b) Other evidence (i.e., from observation) which may suggest drug use within the home;
   c) Other evidence which may suggest that drugs are not used within the home;
   d) The presentation of the children and the adults;

Why is this important within the family court?

Laboratory results from hair strand testing give raw numerical data—such as concentration levels of certain substances. However, interpreting what those numbers mean in a real-world context requires specialist knowledge. An expert can help explain:

• Whether the levels indicate excessive, incidental, or one-time use
• If passive exposure could have affected results
• How factors like hair colour, cosmetic treatment, or hair type may influence findings

Why it is significant for the reports to be treated as expert evidence?

1. Parties can challenge expert evidence by way of further questions in accordance with the Family Procedure Rules.

At Duncan Lewis Solicitors, we deal with various cases whereby clients instruct us to make applications to the court to ask testing companies questions as to the validity of results. If a client believes that the results are inaccurate and could be a result of passive exposure to a specific substance, then we can put this forward. This allows for fairness and transparency.

2. Similarly, if a report is treated as expert evidence then the expert can, in some circumstances, be cross examined at Court. This promotes transparency and holds the expert accountable for their conclusions.

Cross-examination gives us the chance to challenge specific factors, ensuring the court does not rely on potentially flawed or misunderstood evidence. This helps prevent over-reliance on technical findings that might seem definitive but are actually nuanced.

If hair strand testing is not treated as expert evidence and therefore subject to the scrutiny of further questions or cross-examination, incorrect or unclear results may be taken at face value. For example:

• A false positive result might suggest ongoing substance use when there is none.
• A misinterpretation of low-level or passive exposure could be presented as regular misuse.

This can lead to unjustified separation of a child from a parent, contact not being permitted to take place or it remaining supervised which is traumatic and may have long-term emotional and psychological consequences.

Duncan Lewis’ Family department comprises a professional, efficient team with a wealth of experience in dealing with all aspects of Family Law. Our overriding priority is to listen to all of the issues in your case and explore the best way of resolving your problems. For expert legal advice, get in touch today at 03337720409.

About the Author

Courtney Springall is a caseworker based within our esteemed family law team at Duncan Lewis Solicitors, having joined the firm in 2024. Based within the Manchester office, Courtney works under the direct supervision of Solicitor Emily Alice Reed.

Contact Courtney via email at CourtneySp@duncanlewis.com, or by telephone at 02072752807.

Duncan Lewis Solicitors

Duncan Lewis Solicitors' family law team is renowned for its outstanding legal services, and is ranked top tier by The Legal 500 2025 guide, which highlights its dedication to client service. The team covers a wide range of family law areas, including complex international child abduction, special guardianship orders, wardship, surrogacy, adoption, and public law children cases. They are also skilled in handling high-value divorces and cohabitation agreements.