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The pitfalls of hair testing

Date:4 DEC 2014
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Amy Barrow, Trainee, Irwin Mitchell Sheffield
Zoe Round, Partner, Irwin Mitchell Sheffield

Whilst societal attitudes to drug use have evolved over time, our courts continue to preside over an inquisitorial jurisdiction. If there is any suggestion in children law proceedings of parental drug use, the court may direct that a hair test is required before determining the amount of time that a child can spend with that parent.

When your client is faced with the prospect of a hair test and informs you that their drug use is purely historical, indeed they stopped using within the last 6 months, you may assume that a negative result will be a foregone conclusion.

In an increasing number of cases, clients who report purely historical drug use are generating positive test results and being reported by testing companies as moderate, medium or high users. When such a result is received you may think that the client has fallen off the wagon. However, this might not be the case and further investigation is required to avoid any potential miscarriage of justice.

There are many factors that can influence your client’s test results, all of which need to be explored in advance with your client and discussed with the testing company at the time of sampling in the hope of improving the accuracy of the report.
  1. Confirm the nature of the substance that your client has used and whether it has been mixed with any other drugs or chemical agents. This will influence which chemical compounds your client will be tested for. A breakdown of levels for all of the components of drugs groups tested should be displayed in the report.
  2. Confirm what grade of substance and the amount that your client used on each occasion. The purer the substance, the higher the result may be and the longer that it can remain in your client’s system. If your client has used high-purity substances in large quantities, it is conceivable this may remain in their system some months after usage.
  3. Confirm the method of ingestion and whether your client could have been exposed to the substance environmentally, for example by passive smoking or surface ingestion. In Re Y [2014] EWHC 486 (Fam), it was accepted that when a 20-month-old child tested positive for cannabis and was classified as a ‘medium to moderate user’, that the child had been environmentally exposed to the drug by virtue of passive smoking. 
  4. Confirm with your client what medications they have been taking including over the counter and prescription medication. It is important to include everything such as cough syrups, antibiotics and painkillers. Many medications are capable of influencing results. 
  5. Confirm with your client if they have procedures done involving local and general anaesthetics. Many forms of topical anaesthesia such as local anaesthetics contain chemical compounds which are derivatives of cocaine or cocaine like compounds which may impact upon the results.
  6. Confirm if your client chemically treats their hair including using dyes, highlights and styling products. 
  7. When the sample is taken, ensure that the sample is sufficient in weight. Check with the testing company what the recommended minimum weight of each sample should be. If a sample is at an underweight or overweight, this can affect the results.

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  1. Confirm how many months usage your client is being tested for and if a month by month analysis will be done. It is useful to have a month by month breakdown if your objective is to advance a case of historic use. The hair tested is generally in blocks of 1cm, the closest to the root is the latest month of testing and furthest from the root the earliest month of testing.
  2. As soon as your client stops taking drugs, levels will drop quickly in the hair closest to the scalp. However, metabolite levels can remain detectable for some months because of the proportion of hair in the resting (telogen) phase. This phase of hair is not growing and can contain traces of drug and metabolites from previous use.
  3. Instructing solicitors normally witness sample collection. The Society for Hair Testing have sample collection guidelines which most companies adhere to. Check that the sample is being taken using a sterile kit to avoid the risk of cross –contamination.
  4. The tester should gently tug at your client’s hair which may cause discomfort, this will ensure the sample taken is from closest to the root. Ask the tester to use a ruler to ensure that sufficient length is being taken, this enables the testing periods to be more accurately defined.
  5. Clarify with the tester if a B sample will be taken for re-testing in case the results need to be challenged. In Local Authority v AF [2014] EWHC 2042 (Fam), the court cautioned against relying on science alone without regard to the wider picture. It was accepted that even in the relatively mature and sophisticated world of trichological drug testing there is still room for contamination or human error.
  6. Confirm how the samples collected will be sent to the testing company. As a minimum, they should be sent for next day delivery. Any delay could be prejudicial to your client in receiving the results and being able to seek further clarification if necessary from the testing company before returning to court.
Upon receipt of the test results, a cautious approach should be taken in their interpretation. Many testing companies will classify your clients results on a usage scale. It is important to read the small print to identify how this scale has been formulated. Your client’s classification will be based on the drug concentrations found in the hair. Usually laboratories define their scales from a very heterogeneous groups using a wide range of both scalp and non-scalp hair. This renders the classification suitable for general guidance only and should not be the subject of over interpretation by the parties and the court without regard to the wider picture and the fact specific circumstances of each case.