Människan som bevisvärderare - en kognitivt rättsvetenskaplig studie av erfarenhetssatser.

Sammanfattning: In Sweden, the evaluation of evidence is free which means it is not governed by legal rules. When evaluating evidence, the judge uses what the legislator refers to as common knowledge theorems (“allmänna erfarenhetssatser”), which enables the evidence to be put in context. Common knowledge theorems constitute generalizations about how circumstances usually relate to each other and are based on general knowledge and life experience. These theo-rems’ meaning within the process of evaluating evidence is fundamental, because they make the evidence comprehensible. At the same time, the use of theorems leads to information being processed in a partial manner, based on the judge’s knowledge. Many of the theorems that are used within the evidence evaluating process can not to be compared with rules of nature but ra-ther indefinite generalizations. To this should be added that the character of the theorems, being generalizations, also causes a thin line to emerge between what is legitimate on the one hand and what constitutes stereotypical beliefs and prejudices on the other. This thesis main purpose is to give an account for and question both the use and the content of the common knowledge theorems by comparing the method for using them, as it is described within legal theory, with psychological research. Legal theory describes the content and use of the theorems in a way where only acceptable content is a demand and a model that evaluates the theorems applicability and certainty. Because of this there are far reaching requirements on the judges’ ability to evaluate their own knowledges and to calculate on probabilities concerning this knowledge and their applicability at the case be-fore the court. From a legal theoretic perspective alone, it is possible to criti-cize how the acceptable content is described but also the method that described the use of the theorems within the process of evaluating evidence. Social cog-nitive research that accounts for matters on how stereotypes are created, can be helpful to problematize the content of the theorems, which can be compared with stereotypes even further. Such content, concerning social groups, does not need to be a product of an impartial process. Human beings do not register the world as it is, but rather processing of information is partially impaired preconceptions. It is easy to create stereotypical beliefs, but also to create va-lidity for the same beliefs. The method that describes how issues relating to the theorems certainty and applicability should be evaluated can be questioned on the basis of cognitive psychology aimed at people’s ability to make assessments. This kind of re-search describes people’s ability to make assessments and take decisions in an environment containing complex information, which the process of evaluating evidence can be compared with, and shows that models that assume people’s full rationality and ability to calculate exhaustively on probabilities is not rep-resented in how people really think. The human intellect can be described as being two systems, where the first is automatic, intuitive and heuristic-based where the other is analytic and rule-governed. Although we experience our reasoning as conscious, many times people are using the intuitive way of thinking. Also, the intuitive way of thinking can generate biases which leads to that probabilities is judged incorrectly or that our cognition rather tries to confirm a hypothesis rather than to falsify it. In the light of this it is possible to question both the knowledge that is used within the frame work of the common knowledge theorems, but also to question the model that is described to evaluate the accuracy of those theorems.