Introduction The following discussion attempts to provide an understanding of mental illness and how it relates to the law of evidence as it is provided within Ontario Statutes, Canada. There is no doubt that every aspect of law aims at maintaining order within a given society, institution, or nation. It is important that every aspect of individual actions is guided by principles of laws. Laws are governing directives that attempt to ensure harmonious existence within the society. There are so many arms or forms of regulating bodies, law in respect to the various forms of conflicts and disharmonies that exist (Paciocco & Stuesser, 2011). One such arm or form of law is the evidence law. The following discussion provides an in-depth analysis of evidence law whilst trying to relate the same with mental illness. An overview of law of evidence forms part of this paper other than the main analysis.