I am grateful for this very helpful note from Sophie Smith Holland, currently a pupil at St Johns Chambers in Bristol.
This judgment considers the science of hair-strand testing for cocaine and provides practitioners with a useful guide of the process. Further, it considers the way in which expert reports are presented and makes suggestions as to how things could be improved.
The case concerns care proceedings issued in respect of “Holly”. M had a long history of drug misuse and her 3 older children had previously been removed from her care. Holly was removed from M at birth but was later returned. It was agreed that threshold was crossed but M had turned her life around such that she was capable of looking after Holly with support. The only question was whether this arrangement should be underpinned by a care order or a supervision order.
There was also an underlying factual issue: had M been using drugs, albeit at a low level, during the past two years? M accepted that up to July 2015 she had used cannabis daily and cocaine less frequently. She was adamant that she had not used drugs since and all the evidence supported her, except for hair strand tests taken over the two-year period which were showed low-level cocaine use for at least some of the time.
The HSTs were carried out by Alere Toxicology, Lextox and DNA Legal and they were all invited to intervene in the proceedings. Evidence was heard from each of them, an expert for M and a jointly instructed expert.
On 3 March it was ordered that Holly be returned to her mother’s care under an ISO. The issue about the validity of the HST results was transferred to the High Court.
Following Holly’s return, M was seen regularly by her drug support worker who gave her random drug/urine tests. These would detect significant (as opposed to slight) drug use in the previous 3 days or so. 57 tests were carried out between March and July and all were negative.
On 17 July all three testing organisations took a sample to cover a 6 month period. The results showed the presence of very small amounts of cocaine and low levels of BE. The LA argued that complete abstinence had not been achieved (which raised the level of risk that Holly would get caught up in future drug use) and that the results showed that M had not been telling the truth and consequently could not be fully trusted (their plan was for Holly to be placed for adoption but this was changed two days before the hearing(!) to a plan to return to with M under either a care or supervision order).
The Judge’s approach
Mr Justice Jackson started by saying: “Hair strand tests can provide important information, but in order for that to be of 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 they appear as numbers.” [para 25]
He then referred to several cases in which hair strand testing has been considered to assist him in approaching the issues in the case. In brief, the passages referred to say that:
• HST reports should present the analysis in clear language suitable for a lay person
• PD12B applies to hair strand test reports as they are opinion evidence despite being essentially factual
• HST results should be used only as part of the evidential picture. High levels might form a significant part of that picture but the tests should not be used to reach evidential conclusions by themselves in isolation of other evidence
• 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 evidence 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 and the quantity of drug in any given section is not proof of the quantity actually used in that period but is a good guide to the relative level of use (low, medium, high) over time.
Next, he set out 12 propositions agreed between the expert witnesses, which provides a useful guide for practitioners to refer to:
1. Normal hair growth comprises a cycle of three stages: active growing (anagen), transition (catagen) and resting (telogen). In the telogen stage can remain on 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.
2. Human head hair grows at a relatively constant rate, ranging as between individuals from 0.6 cm (or, in extreme cases, as low as 0.5 cm) to 1.4 cm (or, in extreme cases, up to 2.2 cm) 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 1 cm sample and for confusion if overlaying supposedly corresponding samples harvested significant periods apart.
3. The hair follicle is located approximately 3-5 mm beneath the surface of the skin; hence it takes approximately 5-7 days for the 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.
4. After a drug enters the human body, it is metabolised 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 human scalp.
5. The fact that a portion of the hair is in a telogen stage 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 month period thereafter.
6. Hair can become externally contaminated (e.g. through passive smoking or drug handling). Means of seeking to differentiate between drug ingestion and external contamination include:
(i) washing hair samples before testing to remove surface contamination
(ii) analysing the washes
(iii) testing for the presence of the relevant metabolites and establishing the ratio between the parent drug and the metabolite
(iv) setting threshold levels.
7. Decontamination can produce variable results as it depends upon the decontamination solvent used.
8. The Society of Hair Testing (SoHT) has set recommended cut-offs of cocaine and its metabolites in hair to identify use:
(i) cocaine: 0.5 ng/mg
(ii) metabolites BE, AEME, CE and NCOC: 0.05 ng/mg
9. Cocaine (COC) is metabolized into benzoylecgonine (BE or BZE), norcocaine (NCOC) and, if consumed, together with alcohol (ethanol), cocaethylene (CE). The presence of anydroecgonine methyl ester (AEME) in hair is indicative of the use of crack smoke cocaine.
10. Cocaine is quickly metabolised 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.
11. Some metabolites can be produced outside the human body. In particular, cocaine will hydrolyse to BE on exposure to moisture to variable degree, 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 produced only inside the body.
12. 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:
(i) Tsanaclis et al. propose that if the ratio of cocaine in the washing to that in the hair is less than 1:10, this indicates drug use.
(ii) 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.
The test results
• The range of results obtained vary quite considerably. The DNA Legal results for 2016 were in some cases two or three times higher than those found by the other organisations. They reported findings in the low to medium range whereas the rest reported low findings.
• Direct comparison is confounded somewhat by the fact that hair was taken at different times, and that the assumed 1 cm growth rate may not be correct.
• Results may be affected by differences in laboratory equipment and differences in the way the hair is washed before analysis.
• Even when the hair was taken by each testing company at the same time, two labs showed a cocaine result relating to April which was well below the cut-off, whilst the DNA Legal result was just about the cut-off.
Variability of findings from HST doesn’t call into question the underlying science, but underlines the need to treat numerical data with proper caution. The test is only part of the evidence. A very high result may amount of compelling evidence, but in the lower range numerical information must be set alongside evidence of other kinds.
Test results are reported as being within a “range”; low, medium or high. The danger is that the report is too easily taken to be conclusive proof of high/medium/low use, when the actual level of use may be lower or higher than the description. There are physiological variables in relation to hair colour, race, hair condition, pregnancy and body size. There are also variables inherent in the testing process (e.g. different washing practices). Further, the testing companies set out their ranges differently:
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<
How should reports be written in future?
The Judge made 7 suggestions to help the nine accredited hair strand testing organisations working in the family law arena:
(1) Use of high/medium/low descriptor:
This is in my view useful, provided it is accompanied by:
• A numerical description of the boundaries between high/medium/low, with an explanation of the manner in which the boundaries are set should be stated.
• A clear statement that the description is of the level of substance found and not of the level of use, though there may a broad correlation.
• A reminder that the finding from the test must always be set alongside other sources of information, particularly where the results are in the low range.
(2) Reporting of data below the cut-off range:
There is currently inconsistency as 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.
I would suggest that reports 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 particular caution in relation to data that falls below it.
Efforts to understand the significance of tests are hampered by the lack of a common vocabulary to describe results in the very low ranges, Descriptions such as “positive”, “negative”, “indicates that” and “not detected” can be used and understood vaguely or incorrectly. The creation of a common vocabulary across the industry could only be achieved by a body such as the SoHT. In the absence of uniformity, reporters should define their terms precisely so that they can be accurately understood.
(4) Expressions of probability:
The Family Court works on the civil standard of proof, namely the balance of probabilities. It would therefore help if opinions about testing results could be expressed in that way. For example:
“Taken in isolation, these findings are in my opinion more likely than not to indicate ingestion of [drug].”
“Taken in isolation, these findings are in my opinion more likely than not to indicate that [drug] has not been ingested because….”
“Taken in isolation, these findings are in my opinion more likely to indicate exposure to [drug] than ingestion.”
(5) 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.
(6) The FAQ sheet accompanying the report (which might better be described as “Essential Information”), might be tailored to give information relevant to the particular report, and thereby make it easier to assimilate.
(7) 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.
The latter part of 2015 and during 2016
M used cocaine at relatively low and infrequent level and has therefore not told the truth. Although there is evidence of M’s attempts to rid herself of drugs, the almost continuous array of results significantly above the threshold cannot adequately be explained by inadvertent exposure. The pattern is much more consistent with use, although exposure could have been a contributor. Also, the results were not too dissimilar to those from August 2015 when M admitted using drugs.
The period after Holly’s birth
There was weaker scientific evidence in relation to the period after Holly’s birth and given the finding in relation to earlier use, the possibility that M is not telling the truth about the later period cannot be discounted. There have been very regular urine testing and continuous face-to-face contact with professionals and no one has noticed the slightest suggestion of drug use and the interpretations of the toxicologists vary. Taking the evidence as a whole, I am not satisfied that it has made out its case in relation to recent use of cocaine and on balance I am prepared to accept M’s evidence that she has been free of drugs since Holly’s birth.
Holly remained with M, under a supervision order.