Study Explores Why Wrongful Convictions Happen

In the almost 25 years since post-conviction DNA evidence has been used to establish criminal innocence, public perception has been transformed by the realization that completely erroneous convictions are not uncommon, even in cases that land defendants on death row or in prison for life. A new exhaustive social science analysis of many of these exonerations since 1989 has identified ten primary factors that, together, have led to the convictions we now know were wrong.

The study by American University’s School of Public Affairs concludes that it is a confluence of circumstances — and the ultimate failure of prosecutors and/or defense attorneys to mitigate those circumstances — that makes the difference between a “near-miss” in which a person is indicted but never found guilty, and a wrongful conviction.

Some of the worst wrongful conviction cases have been linked to what is known as “tunnel vision,” in which a prosecutor who hones in one suspect has a tendency to reinforce beliefs of that suspect’s guilt, even when the evidence suggests otherwise. In fact, the American University study finds that, surprisingly, it is in cases with the weakest evidence that “tunnel vision” is most likely to be a problem. The scholars explain:

As more resources — money, time, and emotions — are placed into a narrative involving a suspect, the actors involved are less willing or able to process negative feedback that refutes their conclusions. Instead, actors want to devote additional resources in order to recoup their original investment. As a result, evidence that points away from a suspect is ignored or devalued, and latent errors are overlooked. At this point, the police are working to rule in rather than rule out the suspect, and prosecutors have moved from “inspection” mode to “selling” mode. Escalation of commitment contributes and facilitates system breakdown because it dismantles the rigorous testing of evidence that makes the adversarial process function effectively.


To a large extent, the panelists attributed tunnel vision in our cases to a police and prosecutorial culture in which questioning and independent thinking were not valued, procedures were not designed to probe already gathered evidence, and little or no concern was given to learning from past errors. Even if safeguards, such as those mentioned above, are in place, they cannot be used effectively when the officials in the system are blinded by tunnel vision.

The study points out that defense attorneys can also suffer from “tunnel vision” when they fail to question the prevailing narrative. The ten factors that may lead to “tunnel vision” and other iterations of what they call the “perfect storm” are: weak evidence by the prosecution, weak defense (including the use of family witnesses), the prosecution withholding exculpatory evidence, forensic error, inadvertent misidentification of a witness, lying by a non-witness, youth of a defendant, any criminal history by the defendant and the punitiveness of the state. This last factor is particularly noteworthy because it is not at all contingent on flaws in individual cases and thus probably the easiest to address through reform and public education. The study explains:

In a punitive legal culture, police and prosecutors may be more interested in obtaining a conviction at all costs (leading to greater Brady violations, etc.) and community pressure may encourage overly swift resolutions to cases involving serious crimes like rape and murder. Additionally, state punitiveness could contribute to more state actors assuming the defendant’s guilt. This culture eventually works against the defendant, as state agents overlook or under-value evidence that contradicts the assumption of guilt.

While the study, the result of three years of research, provides new social science data that focuses exclusively on what happens to an individual once indicted (a wrongful indictment can be caused by false confessions, eyewitness identifications and other factors), its conclusions and recommendations are not dissimilar from those of many wrongful conviction experts and commissions — that “tunnel vision” is a primary concern, and that formal “checklists,” along with a mechanism for routinely reviewing causes of wrongful convictions, are crucial for reform.