Where an unrepresented accused leads evidence of prior criminal history in support of a defence, the trial judge must explain to the accused the likely prejudicial consequences of that evidence and, if the evidence is admitted, must direct the jury that they are not permitted to reason from the accused's criminal history that the accused is the type of person likely to have committed the charged offence. The failure to take either step may render the trial unfair and result in a miscarriage of justice, even where the Crown case is strong. The question whether a trial judge has power to exclude relevant evidence that an unrepresented accused wishes to lead was left open.
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