This month we are joined by Sarah Branson (Coram Chambers) and Professor James Coulson (Professor in Clinical Pharmacology and Toxicology at Cardiff University).
We discuss the concern that over-reliance on the numbers generated in hair testing can lead to miscarriages of justice. The issue is that the use of a standardised cut-off levels have a racial bias, because the dark melanin in the hair helps to incorporate the drugs in the hair so someone with black hair will have a much higher reading than someone with red or blond hair, even if they have used the same amount of drugs over the same period of time.
James makes the point that in other Courts (like to civil, criminal or coroners courts) it is unusual to have an analytical chemist commenting on the wider interpretation of the result. James agrees that it is very important that evidence is not seen in isolation. James takes us through the information that he would to see in these instructions in the future.
Sarah reminds us that we should start thinking about this evidence as expert opinion evidence rather than elevating the presumptive weight that should be given to the evidence. Sarah directs us to the judgment of Lord Peter Jackson in D, Re (Children: Interim Care Order: Hair Strand Testing) [2024] EWCA Civ 498 (10 May 2024)
During the discussion, Sarah and James refer to:
The incorporation of drugs into hair: relationship of hair color and melanin concentration to phencyclidine incorporation M H Slawson, D G Wilkins, D E Rollins J Anal Toxicol 1998 Oct 22.
The effect of hair color on the incorporation of codeine into human hair. Rollins DE, Wilkins DG, Krueger GG, Augsburger MP, Mizuno A, O’Neal C, Borges CR, Slawson MH.J Anal Toxicol. 2003 Nov-Dec;27(8):545–51. doi: 10.1093/jat/27.8.545.
Cuypers E, Flanagan RJ. The interpretation of hair analysis for drugs and drug metabolites. Clin Toxicol (Phila). 2018 Feb;56(2):90-100.
Forensic Science Internation (2018)