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Why expert interpretation matters in drug  and alcohol testing

Forensic Testing Service Technical Director, Paul Hunter, recently joined David Opie,  host of the Today’s Family Lawyer podcast, alongside Sarah Branson, Barrister at  Coram Chambers, to discuss the role of drug and alcohol testing in family court proceedings.

The conversation explores an important issue that is often overlooked: while laboratory testing provides valuable scientific evidence, results should never be considered in isolation.

Understanding how evidence is obtained, interpreted and applied is essential if testing is to support fair and informed decision-making. Throughout the discussion, Paul and Sarah explain why expert interpretation,  appropriate case context and a proportionate testing strategy are just as important as the laboratory analysis itself.

Key takeaways from the discussion

Drug testing should begin with expert advice

One of the central themes of the podcast is that courts and legal professionals should consider instructing an expert, rather than simply requesting an alcohol or drug test.

Every case is different. By understanding the background, the issues before the court and the questions that need answering, an expert can recommend the most appropriate testing strategy, determine whether testing is likely to assist the case and advise whether additional or alternative testing may be more appropriate.

This approach helps ensure that the evidence produced is relevant, proportionate and capable of answering the questions the court is seeking to resolve.

Test results should always be considered in context

Drug and alcohol testing provides one part of the evidential picture.

The discussion highlights that laboratory findings should always be interpreted alongside the wider circumstances of the case, including the individual’s history, the available background information and, crucially, the impact that any substance use may have on parenting.

Rather than asking simply whether a result is positive or negative, the court should consider what the findings are likely to mean in the context of the case.

Hair strand testing requires careful interpretation

Hair strand testing remains an important forensic tool, but like all scientific evidence, it has limitations that should be understood.

Paul and Sarah discuss factors known to influence the interpretation of results,  including differences in hair characteristics, sample collection, environmental influences and evolving scientific research. These are precisely the reasons why laboratory findings should be interpreted by experienced experts rather than viewed as definitive answers in isolation.

The discussion also reinforces that scientific understanding continues to evolve,  making it important that evidence is considered in light of current knowledge and accepted best practice.

Sometimes additional testing provides greater clarity

The podcast includes a real case example demonstrating how additional forensic testing helped resolve conflicting findings.

Rather than relying solely on hair analysis, further nail testing was undertaken,  providing valuable context that contributed to a different outcome for the family involved.

The case illustrates that selecting the right combination of forensic tests can often provide a more complete understanding than relying on a single result alone.

The objective is to support better decisions

Throughout the discussion, both Paul and Sarah emphasise that the purpose of forensic testing is not simply to generate laboratory results, but to help courts make informed decisions based on reliable scientific evidence.

That means understanding both the strengths and the limitations of the available evidence, ensuring results are interpreted appropriately and recognising when further investigation may be necessary.

By combining robust laboratory analysis with expert interpretation, forensic evidence can provide meaningful assistance while reducing the risk of misunderstanding or overreliance on individual test results.

Listen to the full podcast

The Today’s Family Lawyer podcast explores these topics in greater depth, including the practical challenges of interpreting drug testing evidence in family proceedings, the importance of expert involvement and how scientific evidence should be considered alongside all other information before the court.

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