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Elasticity in Evaluations of Criminal Evidence: Exploring the Role of Cognitive Dissonance

NCJ Number
Legal and Criminological Psychology Volume: 16 Issue: 2 Dated: September 2011 Pages: 289-306
Karl Ask; Marc-Andre Reinhard; Tamara Marksteiner; Par Anders Granhag
Date Published
September 2011
18 pages
This study tested the hypotheses that evidence inconsistent with investigators' dominant theory of a case creates "cognitive dissonance" in investigators and that this dissonance can be reduced through either asymmetrical skepticism for evidence deemed to be unreliable (e.g., eyewitness testimony) or a change in belief about the case when evidence is deemed reliable (e.g., DNA evidence).
Taken together, the two experiments that composed the study indicated that the experience of cognitive dissonance is related to investigators' evaluations of the available evidence; however, the motivational mechanism involved is apparently more complex than expected, as indicated by the fact that some of the researchers' predictions received little support. In the first experiment, participants who received inconsistent witness evidence experienced the strongest dissonance. In the second experiment, these participants were able to reduce their dissonance the most. This may be due to the fact that a relatively high amount of elasticity (tendency to be unreliable) is associated with witness evidence. On the other hand, when faced with DNA evidence that did not fit the theory of the case, there was not strong dissonance in investigators, possibly because there was little choice but to change their beliefs about the case, given the accepted reliability of DNA evidence. Dissonance is apparently elevated when the investigator is faced with deciding whether to change the theory of the case based on evidence that is typically unreliable. In both experiments, law students made a preliminary judgment about the guilt of a suspect in a homicide case; they subsequently received DNA or witness evidence that was either consistent or inconsistent with the preliminary judgment. The extent to which participants changed their guilt judgment, judged the additional evidence as reliable, and felt dissonance were the main dependent variables. 2 tables and 41 references