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The Limitations of Hair Strand Drug Testing (11 June 2024)

Date: 11/06/2024
Duncan Lewis, Legal News Solicitors, The Limitations of Hair Strand Drug Testing

Recent developments in hair strand testing reveal external factors affect results, highlighting the need for caution when drawing definitive conclusions from this method.

When drugs are ingested, the drug's presence in the bloodstream gets absorbed by the hair as it grows. A drug's metabolite, which is created when the drug is metabolised by the body, is detected in the hair as a sign of active intake.

 

Detecting drugs in hair involves identifying both the drug itself and its metabolites, which are produced when the body processes the drug. While some metabolites can be present due to external factors, like exposure to moisture, others are only produced within the body. Hair samples are typically divided into segments corresponding to different time periods and cleaned to remove external contaminants before testing. Wash results may also be considered to distinguish between external exposure and actual drug use.

 

The limitations of hair strand testing for drugs

The family courts have long since determined that using hair strand testing alone is not recommended. In the case of London Borough of Islington v. M and another [2017] EWHC 364 (Fam), Hayden J. made the following statement at para. 32:

 

“‘32. It is particularly important to emphasise that each of the three experts in this case confirmed that hair strand testing should never be regarded as determinative or conclusive. They agree, as do I, that expert evidence must be placed within the context of the broader picture, which includes e.g. social work evidence; medical reports; the evaluation of the donor’s reliability in her account etc. These are all ultimately matters for the Judge to evaluate.”

 

Despite this, experts typically view a test that is higher than the cut-off point for both the drug and the metabolite as proof beyond a reasonable doubt that a parent has overused the substance in question. What's even more concerning is that social workers and parenting assessors frequently mistake drug levels found in hair for information about how much drug use the parent has consumed. For many reasons, this is wrong and harmful. This is because every testing company employs different criteria for classifying whether a sample is high, medium or low. Furthermore, the results obtained from the same hair sample examined by several companies can differ significantly from one another. Typical relevant factors which affect hair strand testing that must be established and accommodated in all cases for reliable interpretation of test results include:

  • Natural hair colour
  • Use of hair treatments such as permanent hair dye and thermal treatments with frequency, where applied on the scalp and hair
  • Exceptional exposure to UV e.g. sunbeds, holidays in hot climates
  • Frequency of hair washing and conditioning
  • Brands of shampoo and conditioners used
  • Swimming frequency (and periods), with or without caps
  • If or when the scalp or body hair was shaved
  • Hair style (straight, curly, tight curls (e.g. Afro Caribbean), dreadlocks, head coverings
  • Living environments periods of exposure to drug, type and profiles of exposure
  • Dates for pregnancy, term and birth

Most hair strand testers still do not routinely conduct a comprehensive inquiry to determine all influencing circumstances and obtain a detailed explanation from the parent providing the hair sample. It is impossible to offer a trustworthy interpretation of the test results without taking this context and history into consideration.

 

The use of cut-off levels

Compared to testing blood or urine, hair poses a substantial problem for hair strand testers since hair is external to the body and susceptible to damage and environmental contamination. Cut-off levels were created to differentiate between drug exposure and active drug use. In certain situations, when levels dropped below these cut-off points, the outcome might be explained by repeated exposure to the drug rather than active drug use.

 

A population-wide screening process was used to determine these standardised cut-off limits. This does not account for every unique aspect and influence that is now recognised to have a major effect on the presence, concentration, and profile of medications in the hair. However, this oversimplified reporting causes numerous outcomes to be misreported, leading to both false positive and false negative interpretations on a case-by-case basis in care proceedings.

 

The relevance of hair colour to hair strand testing

The natural pigment called melanin is what gives your hair its colour. The darker the hair, the more eumelanin, or dark pigment, is present. There is extremely little eumelanin in red and blonde hair. Eumelanin levels gradually decrease with age, causing hair to turn grey or white.

 

What connection does this, then, have to hair strand testing? In short, research indicates that the more darkly haired an individual is, the more likely it is that the drug will be detected in their hair and detected in a hair strand test, this is relevant to the Afro- Caribbean and Asian community who tend to have darker hair.The majority of the industry uses cut-offs to interpret hair strand testing, so this has a big impact.

 

The impact of hair straighteners on drug testing

Heated cocaine produces a pyrolysis product called AEME (anhydroecgonine methylester). As a result, AEME is typically detected in the hair of cocaine users who smoke the "crack" kind of the drug rather than snorting it. It serves as a distinguishing sign between people who use powder cocaine and those who utilise crack cocaine. But since AEME is a by-product of heating cocaine rather than a metabolite of crack cocaine, it cannot prove that crack has been used. According to a 2019 study, thermal hair straightening may cause AEME. It was concluded that the existence of AEME in hair is not indisputable evidence of crack cocaine consumption. Alternatively, the usage of hair straighteners could show that cocaine is present in the hair.

 

Growth rate

Some research results indicated that African hair does grow slower than Caucasian hair. In addition, the increased number of knots intertwining and partial breaks can change the composition of actively growing hair (anagen hair) in comparison to Caucasian hair. This means the proportion of resting hair (telogen hair) and African hair may be higher. What could all this entail for a client undergoing care proceedings? While a Caucasian lady who bleaches her hair and uses crack cocaine may show negative drug results, an Afro Caribbean woman who used cocaine recreationally a few months ago and frequently uses hair straighteners may show favourable results for crack cocaine use.

 

There are several limitations of the current practice of hair strand testing. These limitations cause biases. Practitioners should be aware of those limitations and ensure they are brought to the attention of the court deciding the case.

 

Conclusions, what should we do? Getting it right?

  • If a result is challenged, part 25 questions should be raised of hair strand testing companies.
  • Does the reporting of test results fully comply with latest guidance from:

– High Court?

– The International Association of Forensic Toxicology?

• Is the hair sample representative of client’s pattern of drug / alcohol use?

• Are opinions provided evidence based as opposed to use of Cut-Offs?

• Do the opinions achieve Balance of Probabilities in every case?

• Does the report address the questions presented in each case?

• Were you aware of the use of xx product, what impact might that have on the results?

• Were you aware of the use of thermal hair straighteners, what impact might that have on the results?

Nail testing has shown to be a practical and trustworthy method for determining the long-term use and abuse drug, with precise and accurate results. Since 1984, six studies have been conducted to support the use of nails for drug detection.

 

While sectional analysis is not currently possible with nail testing, it is not as challenging as hair strand testing when it comes to growth rates, hair colour, and product or straightener use.


Nail analysis can complement hair analysis and provide additional information, crucial in many cases for a correct interpretation of the results.


Studies show that most drugs of abuse and pharmaceuticals are detected in nails. If there is a significant dispute, the hair is compromised or there is no hair available, then nail testing should be sought.


For laboratories with extensive experience and case, data from nail testing this additional evidence has been shown to assist the expert in forming opinions that are more reliable.

 

About the Author

Marilyn Edwards is a Supervisor and Solicitor in the Family Law and Child Care Department at Duncan Lewis. Marilyn represents clients in all aspects of Family Law and Child Care matters, she has a broad range of experience in divorce matters, low to medium and high net worth financial remedies following divorce, cohabitation disputes, civil partnerships and pre-nuptial agreements, domestic violence as well as Private and Public Children Act matters and domestic abuse work. She is accredited onto to the acclaimed Resolution Scheme and the Law Society’s Children Panel. She is also a member of Resolutions and Association of Lawyers for Children.  For advice or assistance on a children and family law matter, contact Marilyn by email at MarilynE@duncanlewis.com or by telephone at 02072752611.

 

Duncan Lewis Solicitors

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