Evidence Type and Legal Thresholds: How Causal Attribution Shapes Public Judgments of Reasonable Suspicion and Probable Cause

Abstract Book of the 7th International Conference on Research in Psychology

Year: 2026

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Evidence Type and Legal Thresholds: How Causal Attribution Shapes Public Judgments of Reasonable Suspicion and Probable Cause

Lin Zhou, Richard John

ABSTRACT:

This study examines how evidence type and contextual base-rate cues influence public judgments of police searches under two legal thresholds: reasonable suspicion and probable cause. Drawing on research in causal attribution (Heider, 1958; Kelley, 1973) and heuristic decision-making (Kahneman & Tversky, 1973) the study investigates whether lay evaluations of police actions depend on the perceived causal strength of evidence and neighborhood crime context. Using a 2 (Evidence Type: Direct vs. Circumstantial) × 2 (Crime Context: High vs. Low) × 2 (Legal Standard: Reasonable Suspicion vs. Probable Cause) between-subjects
experimental design, participants are randomly assigned to read short vignettes describing a police search and rate the perceived justification of the action as well as the level of certainty required. It is hypothesized that direct evidence will elicit higher justification ratings than circumstantial cues, and that high-crime contexts will increase perceived justification,
particularly when evidence is correlational, reflecting base-rate neglect. Participants are also expected to apply higher subjective certainty thresholds when evaluating searches under probable cause than reasonable suspicion, though this distinction may be attenuated by
contextual cues. Overall, this research aims to clarify how cognitive biases shape intuitive legal reasoning and public support for police decision-making.

Keywords: Police Searches, Evidence Type, Base-Rate Cues, Reasonable Suspicion, Probable Cause