The High Court has allowed an appeal against a conviction for possessing cannabis with intent to supply. After executing a search warrant at the accused’s home in the Perth suburb of Madeley, police found almost a kilogram of cannabis head material inside the home and three cannabis plants behind the house. The accused’s case was that the cannabis was for personal use and was harvested from two of the three plants. Anticipating that evidence, the prosecution called Detective Sergeant Andrew Coen, who testified that a cannabis plant typically yields 100 to 400 grams of cannabis and that ‘head material’ at the upper range is rare. Following his conviction, the accused appealed, relying on new information that Coen had testified in two earlier trials that cannabis plants typically yield 300 to 600 grams of cannabis head material. After hearing evidence from Coen as to why he had changed his view prior to the accused’s trial, a majority of Western Australia’s Court of Appeal dismissed the appeal.

The High Court (Kiefel CJ, Bell, Keane, Nettle & Gordon JJ) unanimously allowed the appeal. The joint judgment held (at [30])  the factors relied on by the Court of Appeal to dismiss the appeal – that the accused bore the onus of proof on the question of intent, and that the accused had not called his own expert testimony, or objected the Coen’s trial testimony, or that the prosecution’s non-disclosure of Coen’s testimony were understandable – were ‘irrelevant to whether there was a significant possibility of a different verdict if the new evidence had been before the jury’. Nothing turns on whether only Coen’s earlier testimony or also Coen’s testimony at trial is treated as fresh evidence ([31]); either way, Coen’s earlier testimony was ‘distinctly apt’ to improve the accused’s prospects of a favourable verdict.

In particular, the prosecution’s closing address, asserting that the absence of expert evidence supporting the accused’s claim that the material came from two plants, ‘could not properly have been made’ ([34]). As well, the Court of Appeal had no occasion to find that Coen’s testimony on appeal explaining his change in testimony was ‘credible and cogent’; that test is used to assess whether evidence impugning the verdict merits a new trial, not whether evidence sustaining the verdict merits dismissing an appeal ([37]). Rather, the credibility of Coen’s explanation ‘was a matter for the jury in the light of all the relevant evidence’ ([38]). Finally, the distinction drawn by the Court of Appeal between evidence of a ‘typical yield’ (Coen’s trial evidence) and an ‘absolute range’ (Coen’s earlier testimony) ‘not drawn at the trial’; his trial evidence ‘was apt to exclude any possibility of those plants having a significantly greater yield than the upper limit of his typical yield range’. ([41]).

The joint judgment observed (at [27]) that it was unnecessary to resolve the second appeal ground and notice of contention concerning the prosecution’s disclosure obligations. Such a consideration would be ‘distinctly inappropriate’ given the Court of Appeal did not ‘essay a considered statement of the position’ and that a ‘firm conclusion’ is unnecessary to resolve the appeal.

Accordingly, the joint judgment quashed the Court of Appeal’s dismissal of the accused’s appeal and instead ordered a retrial.