Bias of Jurors

Bias of jurors, or juror bias, occurs when a jury's verdicts and sentencing recommendations are shaped by factors other than the legal evidence actually presented at trial, a pattern documented across psychology, criminology and legal studies research. Researchers identify several major categories contributing to juror bias, including demographic characteristics of the defendant such as race, ethnicity, gender, socioeconomic status and physical attractiveness, factors tied to the type of crime charged, and cognitive biases that shape how jurors process the information presented to them; studies typically investigate the pattern through mock jury experiments and through analysis of outcomes in real trials, with most research focused on the United States but additional work extending to the United Kingdom, Canada and Australia. Harry Kalven and Hans Zeisel's foundational 1966 study, The American Jury, surveyed roughly 3,500 criminal trials from the 1950s and found that judges and juries agreed on the verdict about 78 percent of the time, with juries tending toward greater leniency when they disagreed, a difference the researchers attributed to juror sentiments about the defendant or about the law itself rather than to the evidence alone. More recent scholarship has refined the framework: Neil Vidmar, in 2002, categorized juror bias into four types, interest, specific, generic and conformity prejudice, while Lee J. Curley and colleagues, in 2022, identified pre-trial bias, cognitive bias and expert-witness bias as the primary sources of bias affecting jury decisions today.