Once a trial court has convicted and sentenced an accused person, it becomes functus officio and cannot reopen the matter or vary the sentence. The only exception is correction of genuine mistakes under s 201(2) of the Criminal Procedure and Evidence Act, which requires (1) a genuine mistake in the delivery of judgment or sentence, and (2) correction to be made immediately (within a reasonable time). A reconsideration of circumstances or change of mind does not constitute a "mistake" for purposes of s 201(2). Where a court wishes to correct a sentence outside the "immediately" timeframe, the proper procedure is to submit the record to the High Court for review. Any sentencing proceedings, including corrections of sentences, must be conducted in the presence of the accused in open court, as required by s 334(1) of the Criminal Procedure and Evidence Act and principles of natural justice. Failure to do so renders the proceedings invalid.