Admissibility of Expert Evidence and Criminal Practice Direction Part 33A

AuthorAdam Jackson,Michael Stockdale
Publication Date01 August 2015
Date01 August 2015
SubjectHigh Court of Justice
CLJ597852 246..249 High Court of Justice
The Journal of Criminal Law
2015, Vol. 79(4) 246–249
High Court of Justice
ª The Author(s) 2015
Reprints and permissions:
DOI: 10.1177/0022018315597852
Admissibility of Expert Evidence and Criminal Practice Direction Part 33A:
R (on the application of Wright) v the Crown Prosecution Service [2015] EWHC 628 (Admin)
Expert evidence, part 33A Criminal Practice Direction
The present case concerned an appeal by way of Case Stated following the conviction of W for the pos-
session of psilocybin mushrooms, a Class A drug, contrary to s. 5(2) of the Misuse of Drugs Act 1972. W
admitted possessing dried mushrooms which were found during a search of his premises having, by his
own admission, picked them from a field in October 2013. Scientific analysis of the mushrooms was
undertaken prior to the trial which identified them as psilocybin but on the day of the trial a ‘difficulty
had arisen because . . . there had not been an agreement to that evidence by the defence’ (at [40]). In the
absence of any scientific evidence the Crown decided to proceed, relying instead on the evidence of Mr
Forster, a civilian working for the police, who the magistrates ‘found to be an expert in the identification
of drugs’ (at [8]).
Mr Forster testified that he ‘physically examined the substance and identified the mushrooms as psi-
locybin by their appearance based on his experience’ and estimated the street value of the mushrooms to
be £10 (at [8]). He identified that ‘the growing period for psilocybin was July to August but could extend
into September’ and in evidence ‘indicated that the growing period could ‘further extend into October
due to global warming’ (at [9]) although he accepted that his evidence was not corroborated by any for-
ensic (meaning scientific) evidence. The magistrates, relying at least in part on Mr Forster’s evidence,
convicted W who appealed on the basis that the Crown, having failed to ‘rely upon any forensic . . .
[meaning scientific] evidence’ (at [3]), had not discharged the burden of proving that the mushrooms
were in fact psilocybin.
HELD, allowing the appeal and ordering an acquittal, the prosecutor’s decision to proceed with-
out the scientific evidence was a ‘completely erroneous tactical decision’ (at [41]). Whilst the court was
‘quite prepared to accept that evidence is admissible from someone who has a great deal of familiarity
with psilocybin...

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