Marilyn MacCrimmon

What is 'Common' About Common Sense: Cautionary Tales for Travelers Crossing Disciplinary Boundaries

Understanding the process of proof in judicial decision making necessarily involves an appreciation of the operation of commonsense knowledge and reasoning in fact determination. Throughout the history of Western civilization, commentators have recognized the crucial role of common sense in our understanding of the world.3 The central role of common sense is further highlighted by the attempts of artificial intelligence (“AI”) to build machines that can see, move, and act. These efforts confirm that we cannot navigate through life without tacitly drawing upon common sense. Steven Pinker illustrates: You know when Irving puts the dog in the car, it is no longer in the yard. When Edna goes to church, her head goes with her. If Doug is in the house, he must have gone in though some opening unless he was born there and never left. If Sheila is alive at 9 A.M. and is alive at 5 P.M., she was also alive at noon. Zebras in the wild never wear underwear.4

Fact Determination: Common Sense Knowledge, Judicial Notice, and Social Science Evidence

Fact determination in judicial decision making involves common sense reasoning. Triers of fact draw on their knowledge of the law, of the physical world, the meaning of words, and human behavior. Fact determination is a product of interaction between the evidence and the background and experience of the trier of fact. The heterogeneous nature of the stock of knowledge means that we must look to more than one doctrine of law in considering how to regulate the fact determination process, including rules of expert opinion, the doctrine of judicial notice, rules re circumstantial evidence, corroboration requirements and presumptions, plus rules against judicial bias must be considered as well as the large body of common sense knowledge.Increased scrutiny has been called for in the role of common sense knowledge in fact determination. What standards should judges apply in deciding which aspects of common sense knowledge are to be incorporated into their decisions? Two interrelated issues are: (1) When is it legitimate for judges to articulate common sense generalizations either in their reasons or in directions to the jury? (2) When should social science evidence be admissible to modify and expand the “stock of knowledge”?This paper will discuss some of the factors which led to recent scrutiny of the stock of common knowledge underlying factual determinations in judicial decisions and examine the role of common sense knowledge in fact determination. The rule of law and statements of fundamental rights such as the Canadian Charter of Rights and Freedoms, the European Convention on Human rights, and the South African Bill of Fundamental Rights require that fact determination be accurate, fair, impartial and egalitarian. How can this be achieved? There is no universal understanding of the way the world operates and therefore unthinking reliance on common sense knowledge may result in decisions which fail to take into account the life experiences of those adversely affected by the criminal justice system. A first step is to articulate the stock of knowledge to the extent that is possible. Once articulated, a normative standard for distinguishing legitimate from illegitimate social knowledge is necessary. The author explore several legal doctrines and other sources of knowledge that inform this standard and which together can help a judicial decision maker achieve accurate, fair, impartial and egalitarian factual determinations.