Criminal evidence and procedure – Supply of drugs – Opinion and expert evidence – Sheriff's charge. High Court of Justiciary: Refusing an appeal against conviction by an appellant who was found guilty of a charge of being concerned in the supplying of heroin, the court held that the procurator fiscal depute's questions to a police officer with substantial experience in drugs matters, asking whether, in the officer's opinion, the appellant was guilty of dealing in drugs, usurped the jury's function and the sheriff should have intervened; and the sheriff's direction about the officer's evidence being corroborative of the basic findings was misguided: however the directions on the function of the expert in the particular circumstances of the case were adequate, and having regard to the quantity of heroin found and the nature of its packaging, coupled with such evidence as the police officer competently gave, the court was unable to say that a miscarriage of justice had occurred.