The National Institute of Justice recently released their study Predicting Erroneous Convictions which examines why some innocent people are wrongfully convicted while others are acquitted, using a case comparison method rather than a traditional “case study” method. Researchers at American University who compared a group of 260 cases that occurred between 1980 and 2012 where an innocent defendant was exonerated only after conviction with a control group of 200 cases where an innocent defendant was acquitted or had charges dismissed before trial.
Unlike prior studies which have focused on what causes an innocent defendant to be charged, this study’s results can be used to determine what is preventing the innocent defendant from being acquitted or having charges dismissed once in the system. This is a helpful distinction, as it allows a greater focus on criminal defense, forensic practices, and prosecutorial discretion.
A Mixed Method Approach
The study’s quantitative analysis yielded 10 primary factors that led to a wrongful conviction rather than the “near miss” dismissals and acquittals:
- A younger defendant
- A criminal history
- A weak prosecution case
- Prosecution withheld evidence
- Lying by a non-eyewitness
- Unintentional witness misidentification
- Misinterpreting forensic evidence at trial
- A weak defense
- Defendant offered a family witness
- A “punitive” state culture
A qualitative analysis of the data followed in which a panel of criminal justice experts analyzed 39 cases to determine how the ten factors were connected and whether “tunnel vision” (when law enforcement professionals focus more on building a case against one suspect at the expense of ignoring contradictory evidence) played a role.
The final report offers recommendations to prevent future wrongful convictions, including recommendations on defense practice, exculpatory evidence, eyewitness identification, false confessions, forensic error, police misconduct, weak prosecution evidence, systemic failures and tunnel vision. The report emphasizes that the interactions of these factors as much as the individual factors themselves are to blame for systemic breakdowns leading to erroneous convictions. This type of interaction requires a comprehensive approach to reform in order to prevent future errors.
Traditional Wrongful Conviction Factors
Factors that have traditionally been suggested as sources of erroneous convictions, such as false confessions, witness misidentification, and racial bias, appeared at statistically similar rates in both sets of cases. Thus, these factors likely only increase the chance that an innocent suspect will be charged but not the likelihood that the charge will result in conviction rather than dismissal or acquittal.
Forensic Error as a Primary Factor in Wrongful Convictions
As one would expect, this study revealed that errors in forensic evidence were correlated with an increased likelihood of erroneous conviction. However, this study’s results suggest a new perspective on how forensic error impacts case outcomes. Errors in forensic testimony, rather than errors in the actual testing were the most common source of forensic error. Forensic testimony errors include: not providing the jury with key forensic information, overstating the inculpatory nature of evidence, use of inaccurate statistics, and misstating the certainty of results and forensic techniques. The implication is that an emphasis on quality control at the interpretation and testimony stages should be added to previous policy recommendations that have focused on improving quality of forensic lab procedures.
While DNA is a widely respected as a forensic tool, this study found that the prohibitive cost of DNA testing often renders it a tool of last resort, with other less accurate forensic tools like fingerprinting, hair comparison analysis and serology testing being used first.
Recommendations for Improving Forensic Error
- Timeliness: Forensic investigation, especially DNA testing, should be conducted early in a case to rule suspects in or out, rather than later once an investigation gains steam and there is a danger of it being used more to confirm or check what police/prosecutors already believe.
- Training/Education: Prosecutors and defense attorneys need more education about forensic testing techniques and should get clarifications about results if they do not fully understand a report. Police officers in more jurisdictions need to be trained in crime scene investigation and should then be present when technicians are collecting evidence to help direct and expand the search.
- Supervision: Forensic labs should be more closely supervised and have procedures that are peer reviewed. There should be discussions of “near miss” cases, which could follow, for example, in the vein of the morbidity and mortality conferences that the medical community holds to discuss mistakes in patient care.
For more information, watch the forthcoming recording of the Wrongful Convictions seminar given by the report’s authors, found here.