your client is faced with the prospect of a hair test and informs you that
their drug use is purely historical, indeed they stopped using within the last
6 months, you may assume that a negative result will be a foregone
increasing number of cases, clients who report purely historical drug use are
generating positive test results and being reported by testing companies as
moderate, medium or high users. When such a result is received you may think
that the client has fallen off the wagon. However, this might not be the case
and further investigation is required to avoid any potential miscarriage of
are many factors that can influence your client’s test results, all of which
need to be explored in advance with your client and discussed with the testing
company at the time of sampling in the hope of improving the accuracy of the
Confirm the nature of the substance that your client has used and
whether it has been mixed with any other drugs or chemical agents. This will
influence which chemical compounds your client will be tested for. A breakdown
of levels for all of the components of drugs groups tested should be displayed
in the report.
Confirm what grade of substance and the amount that your client used on
each occasion. The purer the substance, the higher the result may be and the
longer that it can remain in your client’s system. If your client has used
high-purity substances in large quantities, it is conceivable this may remain
in their system some months after usage.
Confirm the method of ingestion and whether your client could have been
exposed to the substance environmentally, for example by passive smoking or
surface ingestion. In Re Y  EWHC 486 (Fam), it was accepted that when a 20-month-old child tested positive
for cannabis and was classified as a ‘medium to moderate user’, that the child
had been environmentally exposed to the drug by virtue of passive smoking.
Confirm with your client what medications they have been taking including
over the counter and prescription medication. It is important to include
everything such as cough syrups, antibiotics and painkillers. Many medications
are capable of influencing results.
Confirm with your client if they have procedures done involving local
and general anaesthetics. Many forms of topical anaesthesia such as local
anaesthetics contain chemical compounds which are derivatives of cocaine or
cocaine like compounds which may impact upon the results.
Confirm if your client
chemically treats their hair including using dyes, highlights and styling
When the sample is taken,
ensure that the sample is sufficient in weight. Check with the testing company
what the recommended minimum weight of each sample should be. If a sample is at
an underweight or overweight, this can affect the results.
Confirm how many months usage your client is being tested for and if a
month by month analysis will be done. It is useful to have a month by month
breakdown if your objective is to advance a case of historic use. The hair tested is generally in blocks of 1cm, the
closest to the root is the latest month of testing and furthest from the root
the earliest month of testing.
As soon as your client stops taking
drugs, levels will drop quickly in the hair closest to the scalp. However,
metabolite levels can remain detectable for some months because of the
proportion of hair in the resting (telogen) phase. This phase of hair is not
growing and can contain traces of drug and metabolites from previous use.
Instructing solicitors normally witness sample collection. The Society
for Hair Testing have sample collection guidelines which most companies adhere
to. Check that the sample is being taken using a sterile kit to avoid the risk
of cross –contamination.
The tester should gently tug at your client’s hair which may cause
discomfort, this will ensure the sample taken is from closest to the root. Ask the tester to use a ruler to ensure that
sufficient length is being taken, this enables the testing periods to be more
Clarify with the tester if a B sample will be taken for re-testing in
case the results need to be challenged. In Local Authority v AF  EWHC 2042 (Fam),
the court cautioned against relying on
science alone without regard to the wider picture. It was accepted that even in
the relatively mature and sophisticated world of trichological drug testing
there is still room for contamination or human error.
Confirm how the samples collected will be sent to the testing company.
As a minimum, they should be sent for next day delivery. Any delay could be
prejudicial to your client in receiving the results and being able to seek
further clarification if necessary from the testing company before returning to
Upon receipt of the test results, a cautious
approach should be taken in their interpretation. Many testing companies will
classify your clients results on a usage scale. It is important to read the
small print to identify how this scale has been formulated. Your client’s classification will be based on
the drug concentrations found in the hair. Usually laboratories define their
scales from a very heterogeneous groups using a wide range of both scalp and
non-scalp hair. This renders the
classification suitable for general guidance only and should not be the subject
of over interpretation by the parties and the court without regard to the wider
picture and the fact specific circumstances of each case.