Lay judgements of the probable cause standard.

Much legal discourse has focused on the probable cause standard and the constitutionality of law enforcement searches. Existing case law stipulates that probable cause requires less than 50% certainty in a suspect’s involvement in a crime, and that it should be applied consistently regardless of the crime at hand or type of search in question. Because courts have previously declared probable cause to be a ‘lay’ judgement, this experiment investigated whether lay perceptions of the probable cause standard align with the legal guidelines surrounding it. We assigned 406 respondents to read various scenarios varying by crime (assault, narcotics or robbery) and intrusiveness of search (person, car or home), and judge whether a police officer would be justified in conducting a search. Case law suggests that search decisions should not generally depend on the nature of the crime at hand, but may depend on the invasiveness of the search being conducted. Results suggested that respondents generally made their search decisions in line with these principles, but that they implicitly assumed probable cause to require ‘more’ certainty in a suspect’s crime involvement than case law would prescribe. We discuss the implications of these findings for the perceived fairness of police procedures and its impact on police–community relations. [ABSTRACT FROM AUTHOR]