A distillation of the key points from this important guideline case concerning hair strand drug testing.
On 29th September 2017 after 6 days of evidence, legal argument and submissions Mr. Justice Peter Jackson handed down a Judgment that looked at several key issues that are relevant to practitioners in public and private law family proceedings when dealing with disputed drug hair strand test (HST) results. The Judgment gave a helpful overview of the guiding principles as well as insights into issues such as the significance of differing test results that relate to the same time period and the relevance of positive test results that fall below the cut-off level. The Judge identified 12 propositions that were agreed by all the experts. Finally, the Judge gave guidance as to how hair strand drug test reports should be written.
M was the mother of an 18month old girl. M had been drug hair strand tested by three organisations over a period of two years: ALERE, LEXTOX and DNA LEGAL. M admitted cocaine use up to July 2015, but denied cocaine use thereafter. M argued that the low levels of cocaine detected after July 2015 must have arisen from external contamination (from furniture in the home and the fact that she had a relationship with a drug user). Each of the three organisations reported low level cocaine use after July 2015, though their results differed from each other, to some degree.
The parties all agreed that the child should remain in the care of the mother. The key issue in the proceedings was whether this should be underpinned by a care order as contended by the LA, or by a supervision order as proposed by the mother and supported on balance, by the children’s guardian. The live evidence focused primarily on the drug testing and on the interpretation of the results.
Having heard detailed evidence from the various experts, the court found that contrary to M’s denials, there had been some low-level use of cocaine post July 2015, up until December 2016. The LA failed to prove its case that there was cocaine use after December 2016.
Having made findings of fact in relation to the mother’s drug use, the Judge concluded that neither a care nor a supervision order would be the wrong choice. On balance, the Judge favoured a supervision order. The merits of a care order were undermined by the fact that there had been many changes of social worker and there had been poor communication. A lower level of order and a higher level of responsibility on M would assist her in the rebuilding of her self-confidence.
Issues Addressed In The Judgment
Principles Derived From The Case Law [Para 26]
HST results should be viewed in the context of all the evidence [Para 26]:
London Borough of Richmond v B  EWHC 2903 Fam Moylan J – The tests should not be used to reach evidential conclusions by themselves in isolation of other evidence
London Borough of Islington v M & R  EWHC 364 (Fam) Hayden J – In a case involving issues not dissimilar to those in Re H, Hayden J stated that: “expert evidence must be placed within the context of the broader picture, which includes eg: social work evidence; medical reports; the evaluation of the donor’s reliability in her account etc. These are ultimately matters for the judge to evaluate”.
4 propositions relating to drug hair strand testing:
In this case Baker J endorsed 4 propositions:
- The science involved in hair strand testing for drug use is now well-established and not controversial.
- A positive identification of a drug at a quantity above the cut-off level is reliable as evidence1 that the donor has been exposed to the drug in question.
- Sequential testing of sections is a good guide to the pattern of use revealed.
- The quantity of drug in any given section is not proof of the quantity used in that period but is a good guide to the relative level of use (low, medium, high) over time.
1 evidence, not proof
12 Propositions Agreed By The Experts In Re H [Para 28]
At para 28 Jackson J identified 12 propositions that were agreed between the experts:
- Normal hair growth comprises a cycle of three stages: active growing (anagen), transition (catagen) and resting (telogen). In the telogen stage hair can remain in the scalp for 3-4 (or even 5 or 6) months before being shed. Approximately 15% of hair is not actively growing; this percentage can decrease during pregnancy.
- Human head hair grows at a relatively constant rate, ranging between individuals from 0.6cm (or in extreme cases as low as 0.5cm) to 1.4cm (or in extreme cases up to 2.2cm) per month. If the donor has a growth rate significantly quicker or slower than this, there is scope both for inaccuracy in the approximate dates attributed to each 1cm sample and for confusion over supposedly corresponding samples harvested significant periods apart.
- The hair follicle is located approximately 3-5mm beneath the surface of the skin; hence it takes approximately 5-7 days for growing hair to appear above the scalp and can take approximately 2-3 weeks to have grown sufficiently to be included in a cut hair sample.
- After a drug enters the human body, it is metabolized into its derivative metabolites. The parent drug and the metabolites are present in the bloodstream, in sebaceous secretions and in sweat. These are thought to be three mechanisms whereby drugs and their metabolites are incorporated into the human scalp.
- The fact that a portion of the hair is in a telogen state means that even after achieving abstinence, a donor’s hair may continue to test positive for drugs and/or their metabolites for a 3-6 months period thereafter.
- Hair can become externally contaminated (eg: through passive smoking or drug handling). Means of seeking to differentiate between drug ingestion and external contamination include:
- Washing hair samples before testing to remove surface contamination
- Analysing the washes
- Testing for the presence of the relevant metabolites and establishing the ratio between the parent drug and the metabolite
- Setting threshold levels
- Decontamination can produce variable results as it depends on the decontamination solvent used.
- The SoHT has recommended cut-offs of cocaine and its metabolites in hair to identify use:
- cocaine: 0.5ng/mg
- metabolites BE, AEME, CE and NCOC: 0.05 ng/mg
- cocaine (COC) is metabolized into benzoylecgonine (BE or BZE), noecocaine (NCOC) and if consumed, together with alcohol (ethanol), cocaethylene. The presence of anydroecgonine methyl ester (AEME) in hair is indicative of the use of crack smoke cocaine.
- Cocaine is quickly metabolized in the body: therefore, in the bloodstream the concentration of cocaine is usually lower than that of BE. However, cocaine is incorporated into hair to a greater degree than BE: therefore, the concentration of cocaine in the hair typically exceeds that of BE. Norcocaine is a minor metabolite and its concentration in both blood and hair is usually much lower than either cocaine or BE.
- Some metabolites can be produced outside the human body. In particular, cocaine will hydrolyse to BE on exposure to moisture to variable degrees, although high levels of BE as a proportion of cocaine would not be expected. It is very unlikely that NCOC will be found in the environment. The fact that cocaine metabolites can be produced outside the body raises the possibility that their presence is due to exposure: this is not the case with cannabis, whose metabolite is only produced inside the body.
- Having washed the hair before testing, analysis of the wash sample can allow for comparison with the hair testing results. There have been various studies aimed at creating formulae to assist in differentiating between active use and external contamination. In particular:
- Tsanaclis et al. propose that if the ratio of cocaine in the wash to that in the hair is less than 1:10, this indicates drug use.
- Schaffer proposed “correcting” the hair level for cocaine concentration by subtracting five times the level detected in the wash
The underlying fundamentals are that if external contamination has occurred (and therefore a risk of migration into the hair giving results that would appear to be positive) this is likely to be apparent from the amount of cocaine identified in the wash relative to that extracted from the hair.
Different Test Results Relating To The Same Time Period [Para 37-40]
At para 37 Jackson J noted that the range of results obtained by the different laboratories varied quite considerably. For example, the results obtained by DNA Legal were at times two or three times higher than those obtained by the other two laboratories. Jackson J noted that samples were taken at different times and that the assumed growth rate of 1cm may not be correct. The laboratories use different equipment and there may have been differences in the way that the hair was washed before analysis. At para 40, Jackson J concluded that the variability in the hair strand test results did not call into question any underlying science, but underlined the need to treat numerical data with proper caution. The extraction of chemicals from a solid matrix such as human hair is inevitably accompanied by margins of variability. A very high result may amount to compelling evidence but in lower range numerical evidence must be set alongside evidence of other kinds. Once this is appreciated the variability between one low figure and another falls into perspective.
The practice of reporting test results as high/ medium/ low has come about from clients wishing to understand the results more easily. Jackson J warned against using these reports as conclusive proof of high/ medium/ low use. Two people can consume the same amount of cocaine and yet give quite different test results. Two people can give the same test result having consumed quite different amounts of cocaine. These differences can be the results of physiology:
-hair condition (bleaching and straightening which damages the hair)
There are also variables in the testing process.
There is only a broad correlation between the test results and the conclusions that can be drawn and there may be scope for reasonable disagreement between the experts.
Quantifying High/ Medium/ Low [Para 42]
The different testing organisations use different numerical values when describing the results as high/ medium/ low.
Cocaine Low Medium High
DNA Legal 0.5-0.89 0.89-18.9 18.9≤
Lextox 0.5-1.23 1.23-10.19 10.19≤
Alere 0.5-1.69 1.69- 6.14 6.14≤
The Industry Guidelines [Paras 44-45]
The main guidelines in the UK are those published by the SoHT (Society of Hair Testing) which are based on research by Cooper, Kronstrand & Kintz Frensic Sc Int 2012. The guidelines appear to state that a positive test requires at least a concentration of the parent drug at greater than the cut-off level and the identification of one of the metabolites.
The American body SAMHSA [Substance Abuse and Mental Health Services Administration] and the European body EWDTS [European Workplace Drug Testing Society] require the discovery of cocaine and two further metabolites, in each case above the cut-off level before the test can be considered positive.
It was contended by one of the experts in Re H that there is an ‘agreed international guideline’. This contention was rejected by Jackson J who concluded that the industry standard in this country is found in the SoHT guidelines.
The Significance of findings below the cut-off level [Para 46-48]
Jackson J applied the approach adopted by Hayden J in Re R. Jackson J accepted the evidence of the witnesses from the three testing organisations (Alere, Lextox and DNA Legal) that when one analyses thousands of tests, patterns can emerge that help when drawing conclusions. It would be artificial to ignore data because it falls below the cut-off level when it may be significant in the context of other findings. This would increase the number of false negative reports. All information should be taken into account, with due regard being given to whether or not results passed the cut-off. In relation to results that fall below the cut-off, considerable caution should be used.
With regard to the practice of comparing wash samples and test samples, Jackson J noted that this is not a requirement under the SoHT guidelines and that the testing organisations apply this additional safeguard voluntarily.
The Content And Format Of HST Reports [Paras 25 and 57-59]
Jackson J made reference to Re F (Children)(DNA Evidence)  1FLR 328 and the observations of Anthony Hyden QC that in order for hair strand drug test results to be of any real use, the expert must (a) describe the process, (b) record the results, and (c) explain their possible significance, all in a way that can be clearly understood by those likely to rely on the information. If these important requirements are not met, there is a risk that the results will acquire a pseudo-certainty, particularly because (unlike most other forms of information in this field) they appear as numbers [para 25].
Later in the Judgment Jackson J set out 7 points of guidance relating to the format and content of HST reports:
- The use of high/medium/ low descriptors is useful provided it is accompanied by:
- A numerical description of the boundaries with an explanation of the manner in which the boundaries are set
- A clear statement that the description is of the level of substance found and not of the level of use, though there may be a broad correlation
- A reminder that the finding from the test must always be set alongside other sources of information, particularly when the results are in the low range
- There is currently inconsistency between organisations on reporting substances detected between the lower limit of detection (LLoD) and the lower limit of quantification (LLoQ), and those between the LLoQ and the cut-off point.
Reports should record all findings, so that:
- A finding below the LLoQ is described as “detected, but so low that it is not quantifiable”
- A result falling below the cut-off level is given in numerical form, And that this data is accompanied by a clear explanation of the reason for the cut-off point and the need for caution in relation to data that falls below it
There should be a common vocabulary across the industry of terms such as “positive”, “negative”, “indicates that” and “not detected”. In the absence of uniformity, reporters should define their terms precisely so that they can be accurately understood.
- Expressions of probability:
It would be helpful if opinions about testing results could be expressed in terms of the balance of probability
- Where there is reason to believe that environmental contamination may be an issue, this should be fully described, together with an analysis of any factors that may help the reader to distinguish between the possibilities.
- The FAQ sheet (better described as “Essential Information”) might be tailored to contain information relevant to the particular report
- When it is known that testing has been carried out by more than one organisation, the report should explain that the findings may be variable as between organisations.