How accurate can hair strand tests be?

Often drug and alcohol tests are ordered during the care proceedings process. Parents are required to provide a section of their hair which is tested to consider if they have been misusing substances. It has recently been reported that these results may be being misinterpreted.

Hair-strand testing has been used for many years and is used regularly during care proceedings to provide an overview of drug and alcohol use. If a person consumes a drug, such as cocaine, metabolites are released into their blood stream which subsequently deposits into the hair as a result of consuming the drug. Hair-strand testing detects the metabolites to confirm whether a person has ingested the tested drug. Hair-strand testing allows for a segmented result, highlighting the level of drug use per month, per centimetre of hair.

It has been queried what factors may affect these results, such as race, hair colour, pregnancy and exposure to UV rays. The technical director at Forensic Testing Service Ltd, raised that drug companies are regularly using ‘cut-off levels’ to determine a threshold that someone is considered a drug user. This method is criticised as it does not consider the impact of mitigating factors to drug absorption.

The ‘cut off levels’ system provides a universal threshold and provides little consideration for differing circumstances of the participants. For example, donors with darker pigmentation absorb drugs more readily meaning results can vary between someone who has darker hair and someone who has light brown/ blonde hair even if their drug use is identical. Furthermore, hair growth varies between ethnicities, Asian hair grows faster than Caucasian hair on average and African hair grows at a slower rate. This is particularly important to consider when determining whether a person has achieved abstinence.

In a 2017 Judgement, Mr Justice Hayden wrote that ‘hair strand testing should never be regarded as determinative or conclusion’. He later advises that the expert evidence should be read in conjunction with the other evidence i.e. social work evidence, medical reports and the reliability of the donor’s account[1]. Whilst hair-strand testing is pertinent in care proceedings, it is not without its limitations, and it is important for practitioners to remain alive to those boundaries.

If you are being asked to partake in hair-strand testing due to being involved with social services, we may be able to assist. We understand that this can be very stressful and that is why we are here to help and provide advice. We have experience in assisting parents at all stages of Local Authority involvement. Please contact Johnson Astills at either our Leicester office on 0116 255 4855 or our Loughborough office on 01509 610 312 and ask or a member of the Care Team. Alternatively, you contact us through our free online enquiry form or email us at careteam@johnsonastills.com and a member of our team will be happy to assist you