Why Wasn't O.j. Convicted? Emotional Coherence in Legal Inference Explanatory Coherence Probability Theory Wishful Thinking

This paper evaluates four competing psychological explanations for why the jury in the O.J. Simpson murder trial reached the verdict they did: explanatory coherence, Bayesian probability theory, wishful thinking, and emotional coherence. It describes computational models that provide detailed simulations of juror reasoning for explanatory coherence, Bayesian networks, and emotional coherence , and argues that the latter account provides the most plausible explanation of the jury's decision. In 1995, O.J. Simpson was tried for the murder of his ex-wife, Nicole Brown Simpson, and her friend, Ron Goldman, both of whom had been found with multiple knife wounds. To the surprise of many, the jury found Simpson not guilty of the crime, and many explanations have been given for the verdict, ranging from emotional bias on the part of the jury to incompetence on the part of the prosecution. Of course, there is also the possibility that, given the evidence presented to them, the jury rationally made the decision that Simpson was not guilty beyond a reasonable doubt. This paper evaluates four competing psychological explanations for why the jury reached the verdict they did: 1. Explanatory coherence. The jury found O.J. Simpson not guilty because they did not find it plausible that he had committed the crime, where plausibility is determined by explanatory coherence. 2. Probability theory. The jury found O.J. Simpson not guilty because they thought that it was not sufficiently probable that he had committed the crime, where probability is calculated by means of Bayes' theorem. 3. Wishful thinking. The jury found O.J. Simpson not guilty because they were emotionally biased toward him and wanted to find him not guilty. 4. Emotional coherence. The jury found O.J. Simpson not guilty because of an interaction between emotional bias and explanatory coherence. I will describe computational models that provide detailed simulations of juror reasoning for explanatory and emotional coherence, and argue that the latter account is the most plausible. Application to the Simpson case requires expansion of my previous theory of emotional coherence to introduce emotional biasing of judgements of explanatory coherence. Social psychologists distinguish between``hot'' and``cold'' cognition, which differ in that the former involves motivations and emotions (Abelson, 1963; Kunda, 1999). The first two explanations above involve cold cognition, the third based on wishful thinking involves only hot cognition, but my preferred emotional-coherence explanation shows how hot and cold cognition can be tightly integrated. At first glance, the evidence that …