What is the effect of a magistrate’s refusal to hear evidence or argument?

In a very enlightening case, Rex v. Mahoney [1910] 2 Ir R 695, at 708, Lord O’Brien, L.C.J. is reported as follows: “I wish it to be clearly understood that I am not dealing with a case in which a magistrate so misconducted himself as to refuse to hear evidence or argument. No doubt, in all matters of procedure, the essentials of justice must be observed. It is one of the essential requirements of justice that a charge should be duly formulated; that an accused person should have due notice of it; and that he should be given an adequate opportunity of defending himself. Such matters are not mere formalities; they are the essential requirements of justice.”