New Appeal: On the admissibility of evidence by a witness affected by mental illness

In this determination (DPP v Campion), the Supreme Court granted Campion leave to appeal the Court of Appeal judgment which upheld his conviction for murder. The Court certified the following questions:

(i) In a criminal trial, is expert evidence admissible in relation to a) the competence and b) the credibility of a witness if there is material before the court indicating a real possibility that the reliability of that witness’s testimony may be affected by mental illness?

(ii) If the answer to Question (i) is Yes, and the witness refuses to undergo examination, or is for some other reason unavailable for examination by the parties, should the trial judge stop the trial?

(iii) If the answer to Question (ii) is No, is it a matter to be taken into account by the trial judge in considering an application for a direction?

(iv) If no expert evidence has been adduced, is an appellate court entitled to review the decision of the trial judge to permit the case to go to the jury on the basis of his own assessment of the reliability of the witness?


In November 2007, a jury sitting in the Central Criminal Court found Campion guilty of the murder of Brian Fitzgerald in Limerick in November 2002. The DPP’s main witness was James Martin Cahill, who had earlier confessed to the murder. At trial, Cahill displayed psychopathic traits, admitted to hearing voices and screams inside his head and said that the television spoke back to him. Campion requested a psychiatric evaluation of Cahill. The trial judge ruled that he could not order a psychiatric evaluation, warned the jury about acting on Cahill’s evidence where it was not corroborated and allowed the jury to decide whether the whole of the evidence satisfied them that Campion was guilty. The jury returned a guilty verdict. Campion appealed to the Court of Appeal.

The Court of Appeal (here) dismissed Campion’s appeal. It held that the jury was in a much better position that the CoA to assess the reliability of Cahill’s evidence. The jury had sat through the trial, whereas the CoA had only read the transcripts of evidence [43]. Campion sought leave of the Supreme Court for a further appeal.

Although critical of Campion’s notice of application, the Court determined that he had raised an issue of general importance and certified an appeal limited to the above questions.

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