This decision relates to a trial by judge alone before Hall J. The accused was charged with murder, and prior to the trial, admitted that he had unlawfully killed the victim. However, the defence argued that intent could not be proved beyond reasonable doubt (‘having regard to all the circumstances, including the intoxicated state of the accused’), and that therefore the accused could only be found guilty of a lesser offence ().
During the trial, Hall J was required to determine whether the defence’s expert psychiatric evidence was admissible. This issue arose because the expert opinion was partially based on information which was not supported by sworn evidence. The issue is set out at -:
‘The accused elected not to give evidence. That was his right and no adverse inference can be drawn from that fact. However he did call expert evidence from Dr Victoria Pascu, a forensic psychiatrist.
Dr Pascu interviewed the accused at Hakea Prison and relied on information provided by him for the purpose of forming her conclusions. Some of the information provided by the accused reflected evidence that was otherwise available. However, the accused also provided Dr Pascu with some information, including in regard to his drug and alcohol usage generally and on the night in question, that was either not supported by the evidence or was inconsistent with it. This created an issue as to the extent to which Dr Pascu’s opinions were based upon information that was not supported by sworn evidence. An objection by the prosecution was taken to Dr Pascu’s evidence on this basis.’ (emphasis added)
In essence, the accused’s choice not to give evidence meant that he did not confirm on oath what he had said to Dr Pascu. This meant that some of the foundation of Dr Pascu’s opinion was not supported by any admissible evidence at trial, in that what the accused said to Dr Pascu was hearsay.
During the trial, Hall J decided that the evidence could be led, subject to any findings about weight, because Dr Pascu confirmed that it would be possible for her ‘to exclude the information that had been provided by the accused and to only rely upon the evidence before the court, including the accused’s interview with the police’ ().
Justice Hall provided detailed reasons for his decision in the judgment, concluding that:
‘In this case prior to Dr Pascu being called she was asked whether it would be possible for her to put aside the information that was provided to her by the accused and whether she would still be able to give an opinion as to [the fact in issue]. She advised that she could do this. In these circumstances I concluded that Dr Pascu’s evidence would not be based entirely on inadmissible material and that insofar as she had partly relied upon any information from the accused which had not been confirmed on oath then that would reduce the weight to be accorded to her opinion.’ ()
As the opinion did not wholly rely on hearsay, it was still admissible. The extent of reliance on inadmissible hearsay ‘was able to be explored in cross‑examination and is relevant to the weight to be given to her opinion’ ().
This decision is of interest for the practical application of the (sometimes unclear) ‘factual foundation’ or ‘factual basis’ rule – even the nature of which is still subject to some disagreement, as some regard it as a formal rule for admissibility and others regard it as more of a practical requirement in that an opinion without an admissible factual basis cannot be of any weight. The common law authorities relating to this rule are contradictory, so Hall J’s discussion of the principle is helpful to understand which authorities are to be preferred.
In this regard, his Honour cites at  (inter alia, and apparently with some approval) the following passage from Ipp J’s judgment in Pownall v Conlan Management Pty Ltd (1995) 12 WAR 370:
‘[E]xpert opinion based entirely on inadmissible evidence is itself inadmissible and there is no discretion to admit it. I form this view as to admit such an opinion would be to admit, indirectly, the inadmissible evidence itself. If an opinion, based solely on evidence that the court by law is required to exclude, is itself admitted, the inadmissible evidence would have some influence over the court’s decision. Such a result would defeat the purpose of the law that excludes the inadmissible evidence. If the primary facts on which the evidence is based are not admissible, the opinion is valueless and irrelevant and, in my opinion, should be excluded... It is only when the primary facts upon which the opinion has been based are established that the opinion should be admitted into evidence.
On the other hand, where the expert opinion is based only partly on inadmissible testimony and that inadmissible testimony can readily be ascertained and discarded, the opinion should be admitted subject to weight.’ (emphasis added)
The judgment was delivered on 11 December 2020 and can be accessed here. See especially paragraphs – for discussion relating to admissibility of the evidence.