Criminal adjudication is a core feature in American public life. Trials are considered "the central institution of law as we know it," (1) the "crown jewel" of the legal system. (2) Amidst its multiple purposes, an essential objective of the criminal trial is to determine facts pertaining to the defendant's guilt. Specifically, the trial is designed to serve the diagnostic function of distinguishing between factually guilty and innocent people. The prevailing sentiment within the American polity and legal profession is that the trial is indeed acutely diagnostic. (3) This traditional truism, however, is being challenged by the mounting revelations of false convictions. (4)
This article follows in the heels of an article entitled The Limited Diagnosticity of Criminal Trials (Limited Diagnosticity). (5) Both articles pertain to parts of a larger critique of the criminal justice process that will be published in a book manuscript In Doubt: The Psychology of the Criminal Justice Process (In Doubt). (6) Limited Diagnosticity examined how good fact finders are in determining facts from the types of evidence presented in criminal trials. In other words, how well do juries and judges perform the diagnostic function of distinguishing between factual guilt and innocence? To address this question, that article applied a body of experimental psychological research pertaining to the performance of the tasks involved in the adjudicatory process. (7)
As suggested by its title, Limited Diagnosticity concluded that the cognitive processing involved in discovering the truth in difficult cases is more complex and less reliable than generally believed. (8) One problem with the diagnosticity of criminal adjudication stems from the fact that the evidence that is typically presented in criminal trials is of uneven, and often low, quality. The problems with the integrity of the evidence begin with the fact that criminal investigations are not conducted through best-practice procedures. Courtroom testimony is usually proffered months, sometimes years, following the criminal event, a period during which witnesses repeatedly interact with the criminal process and are subjected to a variety of contaminating sources. As a result, the "raw evidence" perceived by the witness at the criminal event often undergoes editing, embellishment, and alteration. Determining the facts accurately from this "synthesized evidence" is a daunting task, especially given the opacity of the investigative process.
Second, the research examined in Limited Diagnosticity indicated that even if the evidence was reliable, drawing the correct inferences from the most common types of evidence presented in criminal trials is a difficult feat. People have a difficult time judging whether a witness identified the perpetrator correctly, whether a witness's memories of an event are accurate, and whether confessions obtained in police interrogations offer truthful accounts of the suspect's deeds. The research also indicated that alibi testimony can be hard to produce and is often misleading, and that detecting deceit from people's demeanor is often mistaken.
Third, the fact finding task is further hindered by a variety of factors that are inherent to the environment of criminal trials. These include the excessive persuasive attempts by lawyers, exposure to extra-evidential information, the emotional arousal that accompanies many criminal trials, and racial stereotypes. Another hindrance stems from the fact finder's cognitive process itself, namely, the "coherence effect." (9) Fact finders tend to overestimate their performance on the fact finding tasks and to underestimate their susceptibility to biasing factors. In sum, Limited Diagnosticity concluded that factual findings in criminal trials are bound to contain an appreciable level of inaccuracy and they are also vulnerable to manipulation. While faulty factual determinations can result in dropped charges against truly guilty people and even wrongful acquittals, they lead mostly to the prosecution of innocent people. …