Family court warned over unreliable hair strand drug tests

Hair strand testing can decide whether parents keep contact with their children, yet the science behind it has been treated as far less certain than many family cases assume. Emily nearly lost access to her baby after a hair strand test raised alarm, a warning sign for lawyers and judges who fear the same disputed evidence may be shaping decisions across the family courts.

The Ministry of Justice says hair strand testing for drug and alcohol use was carried out by Trimega Laboratories Limited between 2010 and April 2014. The government later warned that results from two private companies were being treated as potentially unreliable after concerns about possible manipulation. That history matters because hair results can look precise while still leaving room for error in collection, laboratory practice and courtroom interpretation.

The current rulebook now sets a higher bar. Practice Direction 25G on toxicology evidence says a court should not admit such evidence unless the laboratory is accredited to ISO/IEC 17025:2017 or ISO 15189, or unless exceptional circumstances exist. The point is not simply whether a strand of hair was tested, but whether the evidence is robust enough to justify the stakes that follow when a judge is deciding if a child should remain with a parent.

That concern was brought into sharp focus in Re D (Children: Interim Care Order: Hair Strand Testing) [2024] EWCA Civ 498. At the Royal Courts of Justice in London, the Court of Appeal said hair strand testing must be assessed in the context of the wider evidence, with its evidential value, reliability and limitations all weighed together. The appeal involved four children aged between 13 and 4, and an interim care order that had been in place since 12 October 2023. Hair samples were taken in October 2023, with reports filed on 23 November 2023 and 29 January 2024.

The judiciary’s Hair Strand Testing Working Group is now considering best practice for how hair strand results are assessed, analysed, interpreted and presented in family cases. For families like Emily’s, the issue is not abstract. A technical report can become a turning point in a child protection case, and unless the science is properly policed, the risk is not just an unreliable test result but a failure of due process itself.