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Tag Archives: false positive

Hair we go again – or blip versus tip


What the heck do we do with hair strand tests following Bristol City Council v AA and Others 2012 ?


I’ve written before about my doubts and reservations that hair-strand testing, particularly for alcohol, is as reliable as those touting it would lead us to believe. (I’m sure that they genuinely believe it to be as accurate as it is claimed, I’m not suggesting any bad faith)


You can find the decision here:-


and this one focusses on the accuracy of drug tests. Let me quickly explain in a Sybil Fawlty (specialist subject the bleedin’ obvious) way, why this is important. If you have a parent in care proceedings (or maybe in private law proceedings arguing about residence and contact) who is suspected of using drugs, or has admitted it in the past and now says they are clean, the Court will be interested in whether these problems are largely behind them, or still to be surmounted. A drug test is done, by taking a sample of hair, and chemically analysed. Just as every person in prison is wrongly convicted of a crime they didn’t commit, so most (but not all) people who get a drug test showing they have used drugs says that the lab have made a mistake. But there are people wrongly in prison, and there are people whose lives have been ruined because a drug test got it wrong.


So anything that helps the Courts determine how much reliance can be put on those tests is a good thing.  (As a sidebar, if you’re interested in research at all, and how the headlines don’t tell you everything, Ben Goldacre’s two books Bad Science and Bad Pharma are very very helpful and useful)


There were two companies involved in this, Concateno, and Trimega. These are obviously competitors. And as so often happens, when a person disputes the results that company A provided, we don’t go back to company A to get them to do a fresh test but run off to company B, who test in slightly different ways, and then end up scratching our heads over what to do when the two tests reach different conclusions.


This one is particularly interesting, since the two companies ended up being Intervenors, and Trimega having concluded that there was a human error with their sampling on this occasion found themselves in a corporate bout of fisticuffs with its main competitor, taking place in a Court room.  Concateno’s case effectively being that Trimega’s error here needed to be ascribed to them and them alone and not to be considered a fault of the hair strand testing process generally if done properly and well (for example, by Concateno)


One can see (particularly if you go back to the sums I did in    which my guesstimate was that about  three and three quarter million pounds was being spent on these tests per year (very back of envelope, I don’t claim them to be super-accurate)  )  that the reputation of hair strand testing as being accurate is commercially sensitive, and Concateno did not want to be ‘tarred with the same brush’ as Trimega  – in that particular case.


[Given that these two companies duked it out in Court over their reputations, I’m not about to start taking sides or making assertions – the questions raised are interesting and I still hope that some proper independent research and systematic analysis will tell the Court and professionals just how reliable hair strand testing is. Anything here is drawn from the case, or is my personal opinion]


Now for the purposes of the care case, once the Court had determined that in that particular instance Trimega had accepted a human error and the Concateno tests were to be preferred, that really concluded matters. But the Court had been worried about human error, and had asked Trimega to do a root and branch review of the process and whether such errors had occurred or could occur in other cases. This was the issue that the High Court were grappling with – whether the family Court was the correct forum for the argument that the two companies legimately wished to have.


They did agree, the two of them, this :-

(1) The science is now well-established and not controversial.
(2) 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.
(3) Sequential testing of sections is a good guide to the pattern of use revealed.
(4) 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.


Concateno argued that proper scrutiny of Trimega’s processes and the root and branch review was necessary, in order for the Court to determine the state of hair strand testing. Trimega argued that Concateno’s interest in this root and branch review was in order to achieve commercial gain over a competitor and to effectively seek a judgment critical of Trimega which could be used to the benefit of Concateno.


Mr Justice Baker declined to embark on the separate hearing about the issue, thus

21. I accept Mr. Pressdee’s submission that the starting point is the overriding objective in para 1.2 of PD12A. The three specific questions which arise are whether the proposed hearing would (1) deal with the case justly, having regard to the welfare issues involved; (2) deal with the case in a way that is proportionate to the nature, importance and complexity of the issues and (3) allot to the case an appropriate share of the court’s resources.

22. As Mr Pressdee surmises, the reason for including the third issue on the agenda for consideration by the President, and for giving the two companies permission to intervene in the proceedings, was the possibility that the discrepancy between the test results provided by Trimega and Concateno was attributable to flaws in the science and therefore called into question the validity of hair testing for drugs. In the event, the reason for the discrepancy is now accepted as being human error on the part of one of the companies, Trimega. The integrity of the science, and the validity of hair strand testing for drugs, is unaffected by this case. There is, therefore, no proven need for a general inquiry into the matter, or for detailed guidance as to how such tests should be carried out or used in court proceedings.

23. Furthermore, I agree with Mr. Pressdee’s submission that this court is not the appropriate forum for any such inquiry. The jurisdiction of the family courts is to determine specific disputes about specific families. It is not to conduct general inquiries into general issues. Occasionally, a specific case may demonstrate the need for general guidance, but the court must be circumspect about giving it, confining itself to instances where it is satisfied that the circumstances genuinely warrant the need for such guidance and, importantly, that is fully briefed and equipped to provide it.

24. The arguments advanced in this case have been littered with references to commercial factors.  I have already referred to Mr. Pressdee’s frank assertion that Trimega had withheld an apology to the mother because it feared that its rival would exploit such an apology for commercial advantage. In this respect, Trimega’s attitude does no credit to an organisation entrusted with the responsibility of providing independent expert advice to the court on matters that will affect the lives of children and families. In his final document, Mr. Tolson on behalf of Concateno frankly acknowledged that “ultimately … both companies have commercial interests in this case which are entirely legitimate”. In circumstances where both interveners admit to commercial motivation, the court cannot be confident that would have all the information at its disposal to provide clear, detailed and objective guidance. Any process designed to provide such detailed guidance would have to allow other interested parties to make representations.

25. There is agreement amongst the interveners as to the four uncontroversial propositions advanced by Mr. Tolson. The court endorses those propositions which, for ease of reference, I repeat here:

(1) The science involved in hair strand testing for drug use is now well-established and not controversial.
(2) 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.
(3) Sequential testing of sections is a good guide to the pattern of use revealed.
(4) 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.

26. For the reasons set out above, however, I decline to sanction any extension of this court process to lead to the promulgation of any more detailed guidance. Such a course would be unnecessary and disproportionate.

27. I am equally unpersuaded that it would be appropriate or proportionate to allow any further share of the court’s limited resources to continue the inquiry into the nature of Trimega’s error. Mr. Tolson describes the report prepared following the hearing before the President as a “whitewash” and accuses Trimega of falsely asserting that the error lay in the collection process to conceal more fundamental flaws in their systems. He sets out the justification for that assertion in considerable detail. Mr. Pressdee denies this allegation and goes into even more extensive detail as to the investigation carried out by Trimega into the cause of the human error in this case. In order to investigate those matters, fully and fairly, the court would in my judgment have to conduct a hearing lasting several days, summoning several witnesses from Trimega for oral evidence, and in all probability commissioning further independent expert evidence. At the conclusion of such a hearing, the court might give a judgment setting out its findings, but no order would follow.

28. I do not regard this court in these proceedings as the appropriate forum for the investigation of these matters. I accept Mr. Pressdee’s submission that the court must be guided by the overriding objective as set out in para 1.2 of PD12A. In my judgment a hearing for the purposes of giving guidance, or investigating the nature of Trimega’s error in this case, would be disproportionate and an inappropriate use of the court’s resources, given the enormous demands on the time of judges of the Family Division.

29. Each intervener makes representations that the other should meet a proportion of its costs in connection with the hearings since November 2011. Trimega were ordered by consent to pay Concateno’s costs up to and including that hearing. In my judgment, no further order for costs is appropriate. It was the court that, for reasons explained above, raised the question whether guidance should be given. The court has now concluded that no such guidance is needed beyond the agreed points set above. It was the court that directed Trimega to investigate and report on its error. Having read that report, the court has concluded that any further inquiry by this court would be disproportionate and inappropriate. Neither of these decisions warrants any further costs penalty.

30. Lest it be thought that this case diminishes the importance of expert evidence in family cases, I conclude by emphasising again that in appropriate circumstances the family justice system requires, and will continue to require, expert evidence to ensure that it makes the right decisions about the future of children. I repeat what I said in Re JS [2012] EWHC 1370 (Fam) at para 47:

“Whilst the courts always have to be vigilant to guard against the proliferation of experts in family proceedings, the court must, in my judgment, always have available to it the necessary expertise to make the right findings in these important and difficult cases.”

As Ryder J has recently observed in “Judicial Proposals for the Modernisation of Family Justice” (July 2012) (at para 41):

“In every case, the judge should be able to say: is your expert necessary i.e. to what issue does the evidence go, is it relevant to the ultimate decision, is it proportionate, is the expertise out with the skill and expertise of the court and those already involved as witnesses by reference to the published and accepted research upon which they can rely and of which the court has knowledge.”

Plainly hair strand testing for drugs satisfies all of these criteria. But as this case illustrates, a high degree of responsibility is entrusted to expert witnesses in family cases. Erroneous expert evidence may lead to the gravest miscarriage of justice imaginable – the wrongful removal of children from their families.



One can quite see why the Court did not want to embark, under the auspices of a family Court hearing, on an analysis of scientific method and rigour and involving two commercial entities, each of whom had fiduciary stake in the outcome of such analysis and interest in not having their major competitor having access to innermost details of process and working.


It does rather leave family practitioners, however, in doubt as to whether this was a ‘blip’ in a particular case, as Trimega claim, or whether it is the ‘tip’ of an iceberg about mistakes in Trimega’s process as is hinted at by Concateno.  We do not know.  We won’t know until this next becomes an issue in the case and the Court genuinely does have to determine it.  You can be fairly sure that in any case where both are involved, one of them will be claiming to be more accurate than the other.


And it will leave a family Court in difficulties in how to determine whether a parent who claims that the lab have got their case wrong is genuine or not.


As said earlier, some proper independent rigorous analysis of how accurate the process is – and particularly what the genuine stats for false positives and false negatives are, is vital, if the Court are going to rely on this evidence to make critical decisions about where a child lives.  It would not amaze me to see, over the next few weeks some negative advertising alluding to this case.