Hayden j has just handed down Iago’s offer

“But yet, I say,
If imputation and strong circumstances
Which lead directly to the door of truth
Will give you satisfaction, you may haven’t.”

Mr Justice Baker in Bristol City v A [2012] EWHC 2548 Fam, [2013] 2FLR 1153 considered that the science involved in hair strand testing “is now established and not controversial”. The Laboratory methodology might be – but, as a most recent case has noted, there is still much discussion to be had over the interpretation and the weight of the scientific contribution in the broad canvas of evidence.

Before Hayden J gave his judgment in R (a child Care order) [2017] EWHC 364 on the 30th January 2017, there had been strong guidance on this area of drug testing and the role of experts by Moylan j in LB Richmond upon Thames v B & CB [2011] 1FLR 1345. Hair strand testing should never be considered conclusive or determinative. The expert evidence should be placed within the context of the wider picture which includes the social work evidence, medical reports and an evaluation of the parental evidence.

Hayden j, however, had to grapple with a clear scientific dispute about the interpretation of hair strand tests. On one side of the argument was a prestigious French professor, Pascal Kintz, of “DNA Legal” past president of the Society of Hair Testing. He had a firm view that the SOHT Guidelines required a rigorous and rigid interpretation.

A positive test requires two of the following indicators: a concentration of the parent drug above the cut-off level; an identification of the metabolite (breakdown substance); the presence of some specific minor metabolites highly suggestive of the parent drug.

Without those factors he argued it was not permissible to record a result of ingestion and abuse. Thus if metabolites only are recorded and no parent drug, he would record a negative.

It was noted that the cut-offs in the SOHT were settled with a scientific consensus that allowed the lowest number of false positives and false negatives. The rate of false negatives/positives survives at about 10%. The testing is a blunt instrument for determining frequency and the quantity of ingestion as the donor physiology has a major effect. Hair treatments can also skew testing.

This side of la Manche, Dr Ramsay (Alere Toxicology) and Ms John (Letox) provided a consensus that this rigid interpretation was the wrong approach.

The test results showed Cocaine below the cut off and metabolites for the 2 months (1-3cm sections of hair, months 2&3) and Methamphetamine (crystal meth as a parent drug) in all 3 sections but with no metabolite (amphetamine). MDMA showed up in one section with no MDA metabolite.

“DNA legal” would interpret this as a negative for ingestion as the cocaine was not above cut off and the Cmeth showed no body breakdown metabolites. All it showed, said the professor, was the possibility of contamination from environment while not absolutely ruling out ingestion. The results say nothing about whether the absorption/ingestion was deliberate or knowing.

Hayden j accepted the UK experts’ view. The MDMA low result was a possible for ‘contamination’ as it was to show that insufficient MDMA had been metabolised if ingested. The view accepted was that the meth reading was so significant (3 sections) that it showed a result more consistent with gradual decreasing use over a period. The concentration of 5% in the metabolite of cocaine was strongly suggestive of metabolising within the body from ingestion.

There was a discussion of urine tests taken at the same time which showed no traces – intermittent use may throw negatives in urine but cumulative positives in hair.

Finally the judge factored in all the evidence and the credibility of the Mother, finding that the scientific view of ingestion was supported on the broad canvas of the evidence.

Two final warnings from experience of these cases: be aware that drugs like Spice, Black mamba, Gina* and nitrous oxide gas and other street available drugs may not be detectable either in urine after a few hours/days and not in hair at all. Street-wise clients who are being asked for tests know this. You may have a client with very disturbed functioning or psychotic symptoms from what they see as “undetectables” or from the terrible fact of street drugs cut with poisonous or pycho-active and destructive substances. What may be interpreted as a mental health decline, in the absence of positive drug tests, may be attributable to these undetectables or psychoactive contaminants.