Why hair strand analysis should be instructed as expert opinion evidence

When a parent or guardian is suspected of substance abuse, solicitors or local authorities will often order a hair strand test.

However, what many believe to be a simple “yes or no” drug test is, in reality, far more complex.

More than 15 years of UK case law tells us that hair strand analysis must be treated not as a binary test, but as a form of expert opinion evidence.

To do otherwise risks miscarriages of justice, potentially leading to a child being left in a dangerous environment or wrongly placed in care based on flawed information.

Fact vs. Expert Opinion: A key distinction

In the courts, factual evidence consists of objective, verifiable data. In hair strand analysis, this would consist of the test results’ raw data: which metabolites or chemical compounds were found in the sample, along with their concentration levels.

Many companies that offer hair strand testing report their findings using a binary “positive” or “negative” system based on arbitrary Society of Hair Testing (SoHT) cut-off levels. They will produce a certificate of analysis that fails to provide any interpretation of the results, and therefore fails to reflect the nuances of the case.

Data presented this way, without interpretation, is meaningless. This is where expert opinion evidence comes into play.

An expert will interpret these facts, providing a reasoned opinion on what the findings mean in the context of a specific case.

As Judge Peter Jackson said in the case  Re H (A Child: Hair Strand Testing) [2017] EWFC 64, in order for hair strand tests to be of real value, an expert must describe the process, record the results, clearly explain their possible significance, and fully and faithfully report all findings.

An expert therefore doesn’t just list test results; they contextualise and explain what they mean. Are drugs found in the hair a result of active ongoing use, or is there another reason?

Expert reports and witnesses will consider the client’s complete background, including their declared history of substance use, their living situation, such as if they live with another substance user, and any other relevant factors that could influence test results.

By doing so, the expert can provide the courts with an informed, holistic opinion on the likelihood of personal consumption versus environmental exposure. Without this contextual analysis, the court is left with an incomplete picture, making it impossible to reach a conclusion “on the balance of probabilities”, the standard of proof required in care proceedings.

How FTS champions expert opinion evidence

At FTS, we know that hair strand analysis is too important to be treated as a simple test. We are committed to approaching it as expert opinion evidence from the outset.

First, we ensure a robust and verifiable chain of custody, from the moment a sample is collected to when it is analysed in our accredited laboratory. Our sample collectors are trained professionals who follow strict procedures to avoid contamination.

Second, our analysis goes beyond just providing numbers. In line with successive court rulings, we report all findings, no matter how small, and our expert reports contextualise these results.

We work closely with solicitors and local authorities, providing detailed questionnaires to gather relevant background information about the client. This includes factors such as their lifestyle, living conditions, and declared history of substance use.

Finally, our reports go beyond simple certificates of analysis. They are comprehensive expert opinions that explain the meaning of our findings, considering every potential factor and their possible significance. We can also provide expert witnesses to explain results in court proceedings.

How should local authorities and solicitors approach hair strand testing?

Instruct this evidence properly. Hair strand analysis should be instructed as any other expert opinion evidence would be instructed. If you are unsure how to do this, FTS can help with suggested letters of instructions and wording.

Ensure your client’s full forensic history is taken and is properly accounted for in the analysis. This should include details about a person’s declared use, as well as information about their living conditions, hair condition and treatments, and other relevant factors such as hair colour, race and ethnicity.

Don’t accept reporting that uses Society of Hair Testing cut-off levels, which present results in a binary way and often omit findings below SoHT guideline levels. FTS reports all findings and what they might mean, so the courts have all the relevant information needed to make a decision.

Social workers and legal professionals should be empowered to challenge hair strand analysis:  FTS can provide support with questions that we recommend are always asked of the solicitor instructing or within court proceedings.

When it comes to decisions about whether a child is to be put into care, instructing hair strand analysis as expert opinion evidence is the most responsible and legally defensible way forward.