1. Yes, a magistrate can sit on a criminal case where the magistrate knows one of the principal witnesses for the prosecution. In general, whether a judge or magistrate knows a witness is not considered a material fact relevant to the fairness of the trial. If knowing a witness was considered a relevant issue for a magistrate it would mean that very few trials would take place at Magistrate level in Northern Ireland as Magistrates would invariably know someone appearing before them. Some element of bias would have to be shown before a successful application to have the Magistrate recuse himself could be made.
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