What are the Mohan criteria? Outline the four criteria and identify a potential problem with them.

a.   The Mohan criteria are the Canadian criteria which outline factors that should be considered when determining the admissibility of expert testimony in court. The four criteria are:
•   The evidence must be relevant.
•   The evidence must be necessary for assisting the trier of fact (i.e., it goes beyond the common understanding of court).
•   The evidence must not violate any rules of exclusion (i.e., it must not relate to whether a witness is telling the truth).
•   The testimony must be provided by a qualified expert.
b.   These criteria are potentially problematic as they are highly subject to the discretion of the judge and judges can sometimes be wrong (e.g., the judge determines if the evidence actually goes beyond the common understanding of the jury).