Where an unrepresented accused is charged under s 70(1)(b) of the Criminal Law (Codification and Reform) Act with having sexual intercourse with a young person, the trial court must advise the accused of the statutory defense under s 70(3) which requires the accused to prove on a balance of probabilities that he had reasonable cause to believe the young person was over 16 years of age. Failure to so advise constitutes a misdirection. Where a material witness's evidence is essential to the just decision of a case, particularly regarding a statutory defense, the trial court must exercise its power under s 232 of the Criminal Procedure and Evidence Act to subpoena that witness mero motu. When a trial court bases a conviction on its assessment of a complainant's physical appearance to determine age, it must record the factual basis for that assessment (such as stature, build, physical development, demeanor, sophistication) - a mere personal opinion without supporting factual evidence carries little weight.