Assessing the empirical upside of personalized criminal procedure

Though personalization of law is often viewed as a new idea, pockets of criminal procedure already tolerate it. Many courts have held that Miranda warnings must be tailored when read to juveniles or people with limited English proficiency; a suspect's age is necessarily part of the judicial calculus when determining whether the police's questioning of her is a custodial interrogation; and some state courts consider a person's demographic characteristics when deciding whether they have consented to a search. The question before us now is whether society should go further. Should the law of criminal procedure pay more attention to individual differences in privacy expectations, personality, and cognitive abilities? In this Essay, we adopt an empirical approach, assessing the extent to which the state could meaningfully personalize criminal procedure. Saved for a later day is the normative question of whether it should. We conducted a survey on a nationally representative sample of adult Americans to determine the extent to which factors relevant to criminal procedure law can be predicted by demographic and personality differences. The data revealed that a number of factors predict people's relevant expectations, behaviors, and knowledge. Women consistently perceive less freedom to refuse consent to a law enforcement search, whereas those who have been arrested or have a close friend who has been arrested perceive more freedom to say no. African Americans are more likely to suspect that an officer would draw a weapon or plant evidence in a vehicle during an encounter with the police. Younger and more educated Americans have stronger expectations of privacy against surveillance than older and less educated people. Older and more educated Americans, as well as those who have greater exposure to the criminal justice system, have a better understanding of their Miranda rights than their younger, less educated, and less experienced counterparts. Various ideological and personality factors also correlate with divergent responses. That said, in no instances are demographic and personality considerations hugely predictive. Models incorporating a wide range of predictors typically explained less than 10 percent of the observed variation in individual behavior, expectations, and attitudes. Although we have not tested all approaches to criminal procedure personalization, our empirical investigation of traditional techniques suggests data-driven efforts to personalize criminal procedure may not be worth the trouble. This data-driven approach does shed light on another issue in criminal procedure, however. In a long line of cases, courts have had to decide whether deviations from the standard script for Miranda warnings warranted the exclusion of confessions. We tested several versions of the Miranda warning, including one deemed inadequate in a recent case. We found no differences in comprehension either overall or among respondents at increased risk of misunderstanding their rights (younger respondents and the less well educated). We believe that this experimental approach provides a valuable method of evaluating the appropriateness of nonstandard Miranda warnings.