Chaynee Hodgetts scrutinises the risk of false positive alcohol metabolite testing results
Prior to the pandemic, hand sanitiser was a little-used item, perhaps occasionally found in the bottom of a handbag or gym kit – but, in 2019, its use increased exponentially, to the point of supply chain unavailability. With sanitiser points now readily available in many public places, including transport hubs, public lavatories, workplaces and shops, most people now sanitise frequently during the day, often giving it little thought. It is also now not uncommon to carry a personal bottle of sanitiser, leading to its application being yet more frequent. Furthermore, at many venues, companies and facilities seek visitors sanitise their hands upon arrival. From the perspective of preventing the spread of touch-borne pathogens, this makes sense. But what if there are unintended consequences arising from the now prevalent popularity of sanitiser use – such as in the realm of forensic testing in criminal and family court cases?
This article will first explain alcohol metabolite testing – before highlighting the little-known, but highly significant, effect of hair bleaching on such testing, and the risk of it resulting in false positives. It will then explore a completely novel and original issue, only just developing in the scientific literature – and, to date, not explored in precedent – that of whether hand sanitiser could be leading to false positives in forensic and court-related alcohol testing.
Alcohol metabolite testing
Forensic testing for alcohol metabolites is widely used in both criminal law and family law. Tests relied upon by the courts often identify ethanol metabolites as ‘markers’ or indicators of alcohol consumption in hair or bodily fluids, such as blood or urine. Two of the main markers used are Ethyl Glucuronide (EtG) – and distinctly, Ethyl Palmitate (EtPa) – the latter being a type of Fatty Acid Ethyl Ester (FAEE), the name by which they were formerly commonly referred.
Trusting clients’ attesting – or a testing?
It is normal for practitioners to readily accept a seemingly incontrovertible scientific test result, unless their client’s account explicitly rebuts its validity in any way. However, there are a number of factors – usually ones which fall so far into the scientific to lie beyond the expected expertise of lawyers – which may mean that a seemingly conclusive test result is in fact anything but.
A number of products can potentially lead to false positive test results for alcohol metabolites – not all of which are widely known. This is also an area in which the scientific literature continues to develop – particularly given the recent peak in prevalence of hand sanitiser use among the public. While this article draws upon published and peer-reviewed scientific literature (and notes that this is still an area where the scientific literature is still developing), it is notable that there has been scant discussion of false-positives in the legal literature, or, indeed, in case precedent. Given the gravity of cases which turn upon these issues, and the introduction of the Streamlined Forensic Reporting (SFR) system, this is concerning, not least because of the life-changing potential unintended consequences that result.
Family law forensics
In family law child contact or residence cases, issues can arise surrounding a parent or guardian’s use of alcohol. This is frequently a matter in issue between the parties – especially where a child, or children, have been removed from a parent or guardian’s care or contact on account of alcohol misuse. Often, a condition of the court restoring any degree of contact is the completion of a satisfactory period of alcohol monitoring, through periodic hair or blood tests for a time, before the results are reported, and a hearing takes place to make a finding of fact and/or determine the dispute. The significance of these tests in the context of the case cannot be understated.
The Family Court-approved tests are usually of hair, blood, or urine, and are testing for ethanol metabolites, used as ‘markers’ or indicators of alcohol consumption. Again, the two main markers are EtG and, distinctly EtPa (or FAEE, as it used to be known). The use of hair bleaching or dye can affect both EtG and EtPa/FAEE levels differently.
Dyed in the wool perceptions?
When a test result comes back positive for alcohol metabolites, the courts tend to believe it. Nevertheless, even those administering the tests often ask, as a pre-vetting question, whether certain types of hair dye have been used prior to the procedure. But practices (and responses) vary in reliability. Yet this is a crucial issue, which arguably requires standardisation in elimination.
Use of hair bleaching and dye, in the months prior to hair testing for alcohol metabolites, can artefactually affect the outcome. The effects of this upon EtG and EtPa/FAEE vary. As a starting point, it is worth noting that hair bleaching is generally thought to be associated with lower levels of EtPa/FAEE.
Nevertheless, contrary to any presumption that there might be consistency between the two metabolites, hair bleaching has, on the other hand, been subsequently scientifically associated with false positive results for EtG – with this being affirmed in a Family Court case.
The bleach blonde bombshell
The fact that hair bleaching can lead to higher levels of EtG, and thus, potentially, to false positives for alcohol metabolite testing, is much lesser known. As Moylan J noted, in Richmond v LBC  EWHC 2903 (Fam): “…bleaching will reduce their concentration while the use of products containing alcohol will increase their concentration” (at ).
Interestingly, in 2012, Professor Pragst authored a scientific paper directly based upon Richmond (Pragst, ‘Case Report: Interpretation problems in a forensic case of abstinence determination using alcohol markers in hair’ (2012) 217 Forensic Science International e4-e7), in which his position reflected the possibility for such false positives arising in this way.
In the Forensic Science International case report, interpreting Richmond, Professor Pragst notes: “In a child custody case a mother with a longstanding history of alcohol misuse had to show absolute abstinence for one year. She entered a residential rehabilitation for six months and was tested two months later by way of a hair test for ethyl glucuronide (EtG) with the result of 22 pg/mg in the proximal 0–1 cm segment and the segments 1–2 cm and 2–3 cm being negative. This was interpreted as a minimum alcohol intake of 20–50 units per week in the month before sampling.”
He continued: “Since the mother denied any alcohol intake a second hair sample was collected seven weeks after the first and analyzed for fatty acid ethyl esters (FAEEs) by a second laboratory. A low concentration of 0.03 ng/mg was measured within the 0–6 cm segment of recently bleached hair and was interpreted as showing no evidence of alcohol use during the last six months. Three further hair samples were analyzed during the next nine months with low EtG values (<2.4–3.3 pg/mg, 0–3 cm segment) and low FAEE values (0.27–0.53 ng/mg, 0–6 cm segment). These findings were summarized as indicating continued low alcohol consumption over the past one year period. As a consequence of the conflicting results, the case was dealt with in a hearing before the Family Division of the High Court of London.”
On the matter of hair bleaching, the paper observed that: “From the collection protocol it followed that she [the Mother] had bleached her hair… which was confirmed by approximately 1 cm of proximal dark hair. The bleaching agent ‘‘Nice and Easy’’ contained between many other ingredients hydrogen peroxide and sodium sulfite.”
The paper concluded: “It was concluded in the judgment that the evidence did not indicate that the mother had consumed alcohol in the period tested by the hair samples. It was stated that the evidence in this case highlighted the need for the exercise of considerable caution when hair tests for alcohol are being interpreted and relied upon, both generally and particularly in isolation, and that this case is a proper reminder of the need for expert evidence to be given in a manner according to the Practice Direction.”
The before and after
This demonstrates that, in Richmond, the hair bleaching was associated with increased, higher levels of EtG – not lower, as was the then prevalent perception. However, not all laboratories appear to have caught up with this yet, with an alarming number still suggesting that hair colouring artefactually reduces metabolite levels – when hair bleaching may be leading to false positives for EtG. Where a client has had such testing, the hue of their hair at the time of testing is thus more important than appearances suggest.
In addition, some labs suggest in their reports that EtG can only be found as a result of the presence of alcohol metabolites – inferring that the presence of EtG is virtually a guarantee of alcohol consumption. This is, at best, incorrect – and at worst, inaccurate to the point of risking being misleading. As the 2012 study shows, EtG can be found in cases of use of hair bleach.
This also raises questions of compliance with the Family Procedure Rules (FPR) Practice Direction (PD) 25B at [9.1], in that the use of absolute terms (such as ‘always’ and ‘only,’ without qualification), does not take into account the “range of [scientific] opinion,” as required by PD 25B at [9.1(g)]. In addition, any failure to take into account more recent scientific studies (“material facts”) may amount to non-compliance with PD 25B at [4.1(g)].
In addition to this, how the tests are done can also have an influence on the results. Many labs cut submitted samples of hair into smaller segments for testing – without recording (or reporting) how small these smaller segments actually are. If they are too small, this, too, can invalidate a test. Moylan J noted, again in Richmond: “Professor Pragst said that the published data was not sufficient to establish the validity of testing 1cm sections of hair…” (Richmond v LBC  EWHC 2903 (Fam).
Furthermore, “…no cut off levels have been established or generally agreed for 1cm segments nor, as referred to earlier in this judgment, is there sufficient published data on testing such segments to enable the validity of such tests to be established. Accordingly, any evidence based on the testing of 1 m segments is unlikely to be sufficient to support conclusions as to the level of alcohol consumption” (Richmond v LBC  EWHC 2903 (Fam), at [22[(iv)]).
In Richmond, the possibility of false positives occurring in alcohol metabolite testing is readily acknowledged. As Moylan J summarised: “… as referred to earlier in this judgment [Paragraph ], at these cut off levels, the research evidence suggests that 10% of the results will be false positives…. Finally, on this point, the tests are not designed to establish abstinence or social drinking” (Richmond v LBC  EWHC 2903 (Fam), at [22(iii)]). The reliability of decisions affecting children’s futures based upon such tests thus arguably requires urgent review.
Overall, on the subject of hair bleaching, there is arguably a need for increased awareness among both family practitioners and forensic science labs as to the potential for false positives, which could have life-changing consequences for clients in court cases. However, this is not the only little-known modern false positive risk in the metabolite testing arena.
There is scientific research suggesting that the use of hand sanitiser can, by inadvertent indirect inhalation, lead to the urinary detection of EtG in the body up to six hours after the event, in those abstaining from alcohol.
A study by Arndt et al. (2012) “False-positive ethyl glucuronide immunoassay screening caused by a propyl alcohol-based hand sanitizer” 223 Forensic Science International 359 found false positive alcohol results for EtG in urine “up to 6h after the last sanitiser contact” – and that there were false positives in not only those who had used hand sanitiser, but also in those that had merely inhaled the environmental vapour after others had applied hand sanitiser in their vicinity.
The study added: “similar results are obtained after inhalation of ethanol-based sanitizer vapor. Since ethyl glucuronide is produced even after passive inhalation of such vapors (data to be published), the results are true-positive from the analytical point of view, but false positive regarding deliberate ethanol intake. Moreover, decreased renal function seems to prolong the excretion of ethyl glucuronide and ethyl sulfate… adding another important variable to correct EtG testing.”
This calls into question urine testing for alcohol metabolites undertaken during the covid-19 pandemic, when sanitiser use reached its peak – but to some extent, its relevance remains. The use of ethanol-based hand sanitiser gel on the day of, or immediately before, testing could affect results – potentially leading to another type of false positive result on alcohol tests – this time in urine, for a different type of alcohol metabolite – Phosphatidylethanol (PEth).
Again, some labs suggest in their reports that PEth can only be found as a result of the presence of alcohol metabolites – yet again inferring that the presence of PEth is virtually a guarantee of alcohol consumption – when there can be other causes, such as hand sanitiser use (by the tester, or, most likely, the test recipient).
Many labs seek to eliminate the effects of alcohol sanitising products by confirming the skin cleansing wipes used prior to the blood tests do not contain ethanol. Dermal ontact transfer of any and sanitiser use by the tester is also minimised by the wearing of medical gloves (though their primary purpose is for health and safety). However, this does not mitigate against the risk of the subject’s inhalation of the tester’s sanitiser use – or, more likely, the subject’s dermal absorption, or indirect inhalation, of their own application of hand sanitiser.
A 2019 study, by Augsberger et al. (2019) ‘“Doctor, I do not understand the results of the test, because I swear I am not drinking alcohol.” Truth or lie?’ Toxicologie Analytique et Clinique 066), showed that PEth can be detected in circumstances other than imbibing drink – specifically where ethanol-based hand cleansers have been used (even if they are washed off).
Augsberger found: “An abnormal elevation of PEth concentration in blood was observed after using ethanolic solution for hand cleaning. Thus, ethyl alcohol disinfection have [sic] to be avoid [sic] before blood sampling …. If not, a rapid formation of PEth could happen during blood sampling, involving a risk of erroneous interpretation concerning alcohol consumption.”
Similarly, with urinary EtG, it was reported by Salomone et al. (2018) ‘Occupational exposure to alcohol-based hand sanitizers: the diagnostic role of alcohol biomarkers in hair’ 42 Journal of Analytical Toxicology 157, that: “the regular use of alcohol-based hand sanitizers can affect the concentration of urinary EtG and lead to positive analytical results, particularly when specimens are obtained shortly after sustained use of ethanol-containing hand sanitizer.”
Lastly, on the inadvertent inhalation of alcohol-based products, Hostiuc et al. (2021) ‘Driving under the influence of alcohol during the covid-19 pandemic’ 329 Forensic Science International 111076, found: “some studies revealed a potential effect of alcohol vapors from hand sanitizers on the breath alcohol tests… suggesting they might lead to false positives, at least for 15 min after their use... Almost all alcohol from alcohol-based hand sanitizers (ABHS) is inhaled… Other substances potentially causing false-positive BrAC results in drivers include the use of mouthwash, foods that contain small quantities of alcohol, alcohol-containing nasal sprays etc.”
Additionally, in Emerson et al. (2016) “Effects of alcohol-based hand hygiene solutions on breath alcohol detection in the emergency department” 44 (12) American Journal of Infection Control 1672, it was found: “Among each test condition (foam vehicle with immediate testing, gel vehicle with immediate testing, allowing hands to dry after the use of ABHS, and donning gloves after the use of alcohol-based hand sanitiser (ABHS), alcohol was detected in breath at 1 minute after use of ABHS. Because the use of ABHS by individuals administering breath alcohol detection may result in false-positive detection of alcohol, staff using these devices should consider traditional hand hygiene with soap and water.” This raises some interesting questions about the use of hand sanitiser by those administering breath tests for alcohol.
It would also appear that alcohol-based mist applied near the hair can lead to the detection of alcohol metabolites on hair testing. In Morini et al. (2018) ‘Ethyl glucuronide in hair (hETG) after exposure to alcohol-based perfumes” 19 (2) Current Pharmaceutical Biotechnology 175, it was found: “despite high diagnostic specificity, some cosmetic treatments [alcohol-based perfume] may influence… EtG concentration, leading to false positive results.”
In clean conscience
While the scientific literature on false positive results for alcohol metabolites is still developing, perhaps as an unforeseen collateral outcome of the pandemic, this is a new area of which solicitors practising in criminal and family law should be aware. It may be that instructing a defence expert, where there is a possibility of a false positive result, could assist.
As Moylan J noted in Richmond: “The evidence in this case and these conclusions have highlighted the need for the exercise of considerable caution when hair tests for alcohol are being interpreted and relied upon, both generally and particularly in isolation. Further, these conclusions only emerged during the course of the oral hearing. This should not have occurred as they should have been apparent at a much earlier stage of the proceedings. I regret to say that the hair testing evidence given in this case failed the parties – and in particular the children.” (Richmond v LBC  EWHC 2903 (Fam), at ).
To conclude, again as per Moylan J: “…the potential consequences for the children in this case of the Local Authority’s reliance on the results obtained from the hair sample [are] potentially “catastrophic”. This is … a proper reminder of the need for expert evidence to be given in a manner which accords with the principles underlying the Practice Direction.” (Richmond v LBC  EWHC 2903 (Fam), at ).
Chaynee Hodgetts is our features & opinion editor, honorary lecturer in law and barrister with Libertas Chambers: libertaschambers.com/our-people/chaynee-hodgetts; linkedin.com/in/ch-lawTags:
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