What next for hair strand testing in the family justice system: Re D (Children Interim Care Order Hair Strand Testing)

Sarah Branson, Barrister, Coram Chambers

Sarah Branson is a barrister at Coram Chambers, specialising in acting for children, parents and local authorities in the most complex public law proceedings. These can include non-accidental injury, sexual abuse and serious violence, involving the death of a parent or a child. Sarah also has a thriving private law practice representing parents and children in the most complex disputes.

---

Paul Hunter, Technical Director, Forensic Testing Service Ltd

Paul is an accomplished expert witness in the field of drug and alcohol testing, with over 20 years experience developing and running specialist substance-misuse analytical laboratories. An innovator in the development of best practice since 1999 and subsequently driving improvement in the family court through the provision of forensic investigations of hair and nail samples since 2007, he is a member of the Society of Hair Testing, the London Toxicology Group, United Kingdom and Ireland Association of Forensic Toxicologists and the International Association of Forensic Toxicologists.

---

Racial bias in current practices of hair strand testing

As explained in the June 2023 publication of Family Law (1) the current use of cut-off levels in hair strand testing for drugs and alcohol is misleading and shows alarming racial bias.

You are more likely to face a finding of drug consumption if you have black hair than if you have blonde or red hair. Numerous studies have established that many commonly abused drugs (inc. cocaine and heroin) incorporate into the dark melanin (eumelanin). The more pigmented the hair, the more drug becomes incorporated for the same level of drug use.

In this study by Rollins (2) et al (Table 1) from 2003, all participants were administered the same high dose of codeine (which replicates heroin) at the same time in the same way over the same period and had their hair subsequently tested for both melanin content and the level of codeine incorporated. As outlined in (Table 2), the results are striking. In the sub-category of black hair, it showed significantly higher drug levels among Afro-Caribbean’s compared to Caucasians and significantly higher levels again among Asians compared to Afro-Caribbean’s.

This demonstrates clearly that the application of cut-offs to report HST results are very misleading and should not be relied upon when reports are to be used in the court as evidence. There is significant potential for miscarriages of justice to occur if proper care is not taken to interpret the numbers from these tests appropriately.

Table 1

Cut-off levels

Cut-off levels were developed by the Society of Hair Strand Testing almost 30 years ago, long before the research cited above. They were introduced to distinguish between active use of a drug and environmental contamination of the hair but now known to be a blunt instrument and misleading in many cases. While they may play a role in group testing, i.e. workplace and population studies, they should play no role in the justice system.

Cut-off levels introduce a binary system of reporting test results, i.e. above the cut-off level is positive, reported as chronic use, while below the cut-off drug levels do not get reported, labelled as negative or not-detected, concluding there is no evidence of use. This binary system does not consider any relevant influencing factors or context, such as hair colour, race or ethnicity, hair hygiene, hair treatments, environment and so on. This process completely disregards an experts duty to the court, as established in case law, which requires the reporting of all findings.

It is not for the expert to decide what is and what isn’t relevant to the court.

The guidance from case law demonstrates this process is not suitable for court whilst also highlighting that this area of science is an evolving field. The practice of using cut-off levels in hair strand testing is lagging far behind what s needed in court and analysis of results has not evolved in line with what is now known to impact test results.

 

Table 2

Other challenges with use of cut-off levels

Variation among laboratories

In addition to the racial bias inherent in hair strand testing, there are numerous other problems with the use of cut-off levels.

Independent external quality assessment organisations provide blind hair samples for testing to ensure each accredited hair testing organisation continue to provide reliable test results. The following table (Table 3) highlights the variation in drug levels found across accredited labs from analysis of the same sample of hair.

In many cases, when applying these cut-offs, this variability results in a proportion of laboratories producing a so-called positive result that would conclude use, while the other proportion report a negative result.

Despite this variability being well understood, the testing laboratories continue to apply a defined cut-off to report results.

Historical use

Cut-off levels also fail to consider other relevant information, such as historical use or the environment a former drug user may still be living in.

The table below (Table 4) shows the profile of a previous cocaine user with a history of frequent cocaine use, followed by a period of around 5 months abstinence (the red line shows when drug use stopped).

Despite this donor ceasing use of cocaine around 5 months prior to sample collection (after section 6), when cut-off levels were applied, they continued to produce positive results for cocaine in the five sections that followed. This would have led to the incorrect finding that they continued to abuse cocaine for five months following abstinence.

Table 3

Table 4

Hair treatments

Similarly, other key factors, such as the use of permanent hair dye and bleach, has a significant impact on test results and can lower drug levels in the hair by over 50% from a single application. Repetitive use of these products rapidly degrade the hair structure and can sometimes remove all of the drug from the hair, particularly when thermal treatments are also applied to the hair.

It is sometimes noted in laboratory reports that hair dye can reduce the amount of drug in the hair, taking the level below the cut-off for reporting a positive result. However, while it is brought to the attention of the reader, the interpretation and opinion ignores the potential impact of these treatments. In many of these cases it leads to reporting a negative test result because either a proportion of or all of the drug has been removed. The report would nevertheless conclude there is no evidence of drug use despite this. This can result in frequent users of drugs receiving a negative result.

The following graph (Table 5) is an illustration of this.

Table 5

The use of cocaine in this user was below the cut-off level for the approximate four months from October – January when she declared using significant quantities of cocaine (around £100 a day). This was explained by her multiple use of permanent hair dye and regular use of thermal straighteners during these months, removing cocaine from the hair and leaving only a trace in the oldest hair segment.

Although she stopped using cocaine in January, her cessation of using hair dye led to a spike in the drug level found in the two most recent hair sections. This spike is explained by stopping her use of all hair treatments in early February, leaving a true representation of her cocaine use during the majority of this recent two months. It does however represent a false pattern of her usage as, by application of cut-off levels, it would lead the court to believe she had recently started using cocaine, when in fact her cocaine use had reduced significantly.

This is important as court orders often require those ordered to undergo hair strand testing to not cut or dye their hair. Hair strand testing alone (without proper interpretation) will lead to the perverse conclusion that they have increased or started drug use.

Test results from her nail sample in this case confirmed her declared earlier, very frequent use of cocaine up to late January. It also generally supported her statement that she d reduced her use by around 80% in February and 90% in January. This drop in usage but spike in drugs found in the hair was also explained by the more recent undamaged hair now representing her true cocaine levels during these two months.

In a proportion of cases, the use of permanent dyes can also result in the transfer of drug from the older hair (from previous use) to the more recent hair sections covering periods when drugs were not used. Use of thermal hair straighteners can also transfer drugs from older hair to recent hair from transfer on the plates that become contaminated in users and those exposed to drugs. When cut-offs are applied to report these results, they often produce a positive test result for periods when no use occurred, concluding chronic use, despite complete abstinence during the period tested.

The type of hair treatments, shampoos and conditioners used by the client along with their frequency and period of use are all relevant factors that need to be established and used within the interpretation stage. Many drug testing companies quote the use of such products can affect the result then ignore this information at the interpretation stage by simply applying cut-offs.

In such cases, testing undamaged samples such as fingernails, toenails or body hair is crucial to gain the full picture of abstinence or use. These alternative samples need to be collected when the scalp hair is collected so they are available if required. This will save weeks in the process and enable a more accurate and complete picture from the start.

The guidance in law

How hair strand testing should be approached by the testers

The very recent Court of Appeal authority in Re D (Children: Interim Care Order: Hair Strand Testing) [2024] EWCA Civ 498 (10 May 2024) recognised that hair strand testing is an evolving field and therefore it does have limitations.

Mr Justice Cobb in the lead judgment in this important decision recognised that ‘The variability of findings from hair strand testing does not call into question the underlying science but emphasises the need to treat data with proper caution’. The advocates were also criticised for only presenting the summary findings to the judge, despite the complexity of the case, which led the judge into error. He gave important guidance on how lawyers should approach this evidence (see below).

In respect of best practice for drug testing experts, he also underlined the principles set out by Jackson J (as he was) in Re H (A Child: Hair Strand Testing) [2017] EWFC 64, [2018] 1 FLR 762 that experts need to ‘fully and faithfully explain their findings’.(3)

In Re H (A Child: Hair Strand Testing), the court heard evidence from three different testing companies on what cocaine found in a hair sample could mean. The five experts involved could not agree on whether cocaine use had occurred or not, on the basis that:

‘there are variables in relation to hair colour, race, hair condition (bleaching and straightening damages hair), pregnancy and body size. Then there are the variables inherent in the testing process.’

Despite this knowledge, none of the companies who provided hair testing reports factored these variables into their analysis of the results, they simply applied cut-off levels and drew their conclusions with reference to those.

In light of this, Jackson J set out some important guidance for how testing should work at paragraph 25:

‘Most of the information is factual, and in some cases it will be interpreted by experts, who will express an opinion.  That will be the case when scientific investigations such as hair strand tests are carried out.

These 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 (unlike most other forms of information in this field) they appear as numbers’

When referencing the drug levels and the application of cut-offs, Mr Justice Jackson also provided clear guidance at paragraph 47 that:

‘It would be artificial to require valid data to be struck from the record because it falls below a cut-off level when it may be significant in the context of other findings.’

And at paragraph 59 that reports should record all findings, and 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.

(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.’

He continues at paragraph 41 in correctly identifying that the variables explored above mean that it is not possible to equate the amount of drug found in the hair with usage. Jackson J rightly identifies that:

‘Two people can consume the same amount of cocaine and give quite different test results. Two people can give the same test result and have consumed quite different amounts of cocaine. This is the consequence of physiology: there are variables in relation to hair colour, race, hair condition (bleaching and straightening damages hair), pregnancy and body size. Then there are the variables inherent in the testing process’

These factors are known about and well understood from research and in law.  Notwithstanding this, they are not actively considered within the interpretation stage of report writing. The useful guidance of Jackson J in Re H is still not being applied by the majority of companies undertaking this work who continue to employ cut-off levels to interpret results, despite the evidence base to highlight how discriminatory they are.

This guidance from the authorities can be distilled into the following principles:

1. Hair strand testing is expert (opinion) evidence which will require interpretation by experts.
2. There are variables inherent in the testing process that must therefore be factored into the interpretation of the results.
3. It is therefore necessary for experts to properly explain the significance of the results.
4. The experts must present this in a clear, accurate and unambiguous way in their reports.
5. The classification in reports of ‘high, medium or low’ should not be read to correspond with ‘high, medium or low’ use.
6. No hair strand testing should be regarded as determinative or It must be placed within the broader picture which includes social work evidence, medical reports, the evaluation of the donors reliability in her account.

In short, hair strand testing must be considered expert evidence with the results having been properly interpreted by an expert with reference to all the relevant factors specific to each case.

What is happening in practice?

It is difficult to see how any test conducted without taking a full forensic history from the donor could begin to meet these requirements. Simply determining a negative or positive result with reference to cut-off levels plainly fails. How can a proper analysis be carried out by the hair strand tester, taking into account all relevant factors without that information being obtained?

One laboratory (4) looked at the results of 3,000 samples with known outcomes from declared usage or where other forms of testing (such as nail testing) or other evidence confirmed the conclusions.

When they applied the standardised cut-off levels, the following results were returned.

• ~12% hair samples in cases not using heroin Positive
• ~18% hair samples in cases not using cocaine Positive
• ~22% hair samples from chronic heroin users Negative
• ~20% hair samples from chronic cocaine users Negative
• ~60% hair samples from chronic cannabis users Negative

A rate of 18% false positives is simply unacceptable, particularly when the stakes are so high and the research demonstrates that those false positives are more likely to be from black and ethnic backgrounds as outlined above.

This is further compounded by the fact that AEME5 is often cited as being a marker for crack cocaine use. While AEME is found in users of crack cocaine, the presence of AEME simply establishes the presence of cocaine (be it through use or contamination) that has been exposed to heat. The 2019 study into the use of thermal hair straighteners6 clearly established AEME production in the hair by the use of straighteners. Without a proper forensic history being taken by the expert analysing the hair (to include where on the scalp heat was applied and how often), it is simply not possible to conclude AEME equates to crack cocaine use, and the reports can be dangerously misleading. AEME is not a metabolite of crack cocaine, only a bi-product of heating cocaine.

I still lose sleep over a case of mine over 15 years ago, before the 2019 paper was published, where an Afro-Caribbean client had a positive parenting assessment turned into a negative parenting assessment because it was found she had ‘high levels of crack cocaine’ in her hair, when she was adamant she had only used low levels of recreational powder cocaine.

Many barristers have encountered the dishonest client who lies about drug use. However, without proper analysis and interpretation of what any drugs found in the hair mean, miscarriages of justice continue.

Worse still, sometimes certificates of analysis, which just provide numbers with reference to the cut-off levels, are all that are provided. Presentation of results in this way is again misleading and dangerous. Use of certificates of analysis without proper interpretation is presenting hair strand results in the form of ‘pseudo certainty’ cautioned against by LJ Jackson.

What should happen next?

Drug testing companies should move away from using terminology such as ‘positive’ or ‘negative’ to describe the presence of drugs detected in the hair. As set out above, the presence of drugs within the hair does not necessarily indicate usage, high levels can be found in non-users and low levels or so called negative results are found in regular users, as highlighted in (Table 5).

Despite the authorities above making it clear that hair strand testing is expert evidence, very few tests proceed by way of Part 25 expert instruction, with a letter of instruction being sent which clearly defines what questions need to be addressed and answered in each case.

It is clear that the family courts need to move away from thinking of drug testing as simply a ‘test’ and start to consider it as expert evidence. Re D sets out the importance of presenting the information to the court in a clear and unambiguous way. It is the duty of every expert to not mislead the court. This includes not filtering the evidence by applying an arbitrary cut-off level to test results and reporting tests as negative or not detected when in many cases drugs are present in the hair, they are just not reported.

The use of descriptors such as High, Medium or Low levels are also problematic, but routinely used. These levels vary between laboratories and are often very misleading as shown in (Table 1).

Therefore, when interpreting the drug test results in hair to form an opinion on what they mean, they must have regard for the range of factors that can impact on drugs being found in the hair. These include: their distribution; profile of levels; drug and metabolite ratios across the hair segments tested. Experts also have a duty to keep up to date with advances in science in this fast-developing field.

The letter of instruction should reflect this.

The use of standardised cut-off levels in the interpretation of tests must stop. There are no shortcuts to producing reliable evidence from Hair Strand Testing. Testing laboratories cannot just report results below SoHT cut-off levels in the absence of carrying out a full forensic investigation and analysis, and without reference to previous relevant case data from similar cases to provide statistical significance to support the opinions formed. This issue was highlighted in Re H, where, when asked by the court to report all findings, the experts could not agree on what the results represented because results were both above and below the cut-off when testing the same sample (highlighted in Table 3) and no context or relevant influencing factors were established, and no previous data was available for reference. Therefore the hair test evidence had to be discounted.

Letters of instruction and standard form orders should not be so prescriptive that they prevent the expert from properly assessing the question asked. Expert drug testing is the only area of law where standard form orders tell the expert how to carry out the assessment, e.g., to require three-monthly sections of hair to be tested by sectional analysis for a three-month period of testing.

Instead, if the question posed is ‘what is the existence and extent of drug use for this individual for the last three months’, it may not be possible to answer this without testing more sections of hair than three sections which are assumed to cover the three months of interest. This is because often it is necessary to look at the distribution and pattern of drugs found in the hair over time in order to draw conclusions about drug use. Drugs can be found in the hair sample for many months after usage, due to carry over in dormant hair or transfer from older hair. The only way to therefore distinguish between drug transfer and previous use from active use is to look at the pattern of distribution in the hair over time (highlighted in Tables 4 and 5 above).

The letter of instruction should require the expert analysing the results to take a full forensic history from the individual whose hair is being tested and factor this into the analysis. Anything less than this will lead to relevant and important information not being used at the interpretation stage. This again will lead to the number from the test being treated as pseudo-certainty, which will be misleading in many cases as highlighted in the tables above.

The letter of instruction must also insist that the expert analysing the hair has regard for recent developments in hair strand testing and up-to-date literature and research which could impact the findings. The 2019 research into the effect of the use of thermal hair straighteners on the production of AEME did not immediately appear on hair strand testing reports (and was not factored into the reporting) when the existence of this research was well known. If the expert analysing the results is to have regard to emerging research (as a paediatrician or radiologist would be required to) the court is always getting the most up to date and accurate interpretation.

Toenail, fingernail and body hair should always be collected and, where required, tested to provide a fuller and more holistic picture, particularly in cases where influencing factors come into play. When required, additional testing should be considered for other markers such as melanin content to understand incorporation levels. Oxidative markers produced when hair is damaged can also provide an objective assessment of whether the hair is compromised and likely or unlikely to produce representative results.

If hair strand evidence is key to the resolution of a case, as it often is, forensic experts should be asked to attend professionals meetings or experts meetings so that relevant but possibly missed or misunderstood information can be shared and clarified. For example, an assessing social worker might be aware that a grandparent is a suspected user/dealer of cocaine and the mother a regular visitor to that home. An equivocal result (either use or exposure) might be clarified with that information.

Of course, the case law makes it very clear that hair strand testing analysis should never be used in isolation and should be looked at in the context of wider evidence such as social work evidence and the reliability of the donor s account. If hair strand testing is to play any part in the forensic process within the family court system, it does need to be reliable, properly interpreted and presented, and not discriminatory.

The case law is clear but sadly has not been translated into practice.

What can we do as lawyers?

The Court of Appeal in Re D has provided a clear and unequivocal guidance for what lawyers must do when presented with this evidence as following, taken from paragraph 58 of the judgment:

1. 58. In all cases involving this type of evidence, it is vital that the advocates

i)Draw the judge s attention to what the science can and cannot tell you, as explained in Islington v M and Re H;

ii) Carefully examine the hair strand test reports in full; as far as it is thought helpful or appropriate to do so, they should distil their contents accurately so as to provide with judge with a reliable summary, not just a rehearsal or précis of the general Summary or Opinion section;

iii) Assist the judge to consider the hair strand test results in the context of the whole of the evidence, including:

a. The statements of those who are alleged to have exposed the children to the drugs identified;

b. Other evidence (i.e., from observation) which may suggest drug use within the home;

c. Other evidence which may suggest that drugs are not used within the home;

d. The presentation of the children and the adults;

e. The history of the family generally.

This is all the more important, of course, in cases where the test results are in the lower range.’

It is even more crucial to assist the court in properly understanding the hair strand results in the context of the whole evidence if the testing company has not done so when analysing what any drugs found in the hair might mean. If the testing company has not taken a full history, but simply analysed the results with reference to whether they are above or below the cut off level, it will fall to the barrister seeking to challenge and the court to consider the wider evidential picture.

Hair strand testing is opinion evidence. It should never be approached simply as ‘the science’. It can and should be challenged.

Questions should be asked about the whole process. All matters should be properly evidenced.

If there is a dispute about when an individual stopped using drugs, has a proper analysis been carried out considering the factors that are known to influence the hair segments tested? Has there been photographic evidence provided about how much hair was left on the scalp at the collection stage? Where on the scalp was it obtained from? Has the client previously shaved their scalp, and if so, when?

All these factors will influence the results and the interpretation and opinions formed. Has the expert taken a forensic history and factored in relevant matters such as environment, hair products, dye, pregnancy, ethnicity? If conclusions are drawn about the use of hair dye, what hair dye was used, what impact has it had on the hair, if any, and what is the level of any degradation in the hair? How was this tested? Has the use of hair straighteners or dye led to a redistribution of drugs along the hair shaft, distorting the results?

If head hair is compromised, or no head hair is available, the use of specifically selected nails and or body hair should be utilised for testing. Although it is not possible yet to sectionally analyse body hair or nails, simple measures such as shaving the arm and collecting samples at defined intervals can produce accurate testing periods. Testing a toenail and a small fingernail can in a proportion of cases provide differentiation between historic and recent use.

If there is a dispute about what the presence of drugs in the hair means? Have the relevant influencing factors (identified above) been considered? How? Or have cut-off levels simply been employed?

Lawyers are unlikely to accept a disputed paediatric report in the case of a head injury case at face value. We are likely to read around and try to find a way to mount a challenge. Too few lawyers approach hair strand testing in this way.

We hope this article provides a toolkit for doing so.

Article published in Family Law (August 2024). 

 

Article References: 

1 June [2023] Fam Law 669 ‘Recent scientific developments in hair strand testing and racial bias in current practice of hair strand testing’

2 Journal of Analytical Toxicology. 27 November/December 2003, Douglas E Rollins et all.

3 paragraph 48, Re D [2024] EWCA Civ 498

4 Forensic Testing Services

5 AEME is a chemical found when cocaine is exposed to It is not a metabolite of cocaine (i.e. something that is produced when the body breaks cocaine down), and is not produced solely from smoking of cocaine but often cited as a marker for crack cocaine use.clearly est

6 AEME production in cocaine positive hair after thermal hair treatment , Forensic Science International 302 2019, Nicolas Gambier, Jenny Warling, Nicolas Van Elsue, Michel Yegles.