Canadian Criminal Evidence/Opinion
When a witness is put on a stand their primary role is to recall their knowledge of some past event at issue in the case. As a general rule no witnesses are allowed to give any opinion. However, in practice, the line between fact and opinion can never be clearly drawn, so often exceptions will be made. Opinion, in certain cases, can even be useful to the trier of fact in coming to their conclusions. Experts are generally allowed to give their opinion in matters within their expert knowledge that the trier cannot easily deduce themselves. To address these situations the law of opinion is divided into two area: lay opinion and expert opinion.