Counterfactual thinking and hindsight bias have each generated separate, substantial bodies of research and provided insight into some areas of legal decisionmaking. Counterfactual thinking takes place when people make "if only" comparisons of actual outcomes with imagined alternative outcomes that could have occurred but did not. Hindsight bias is the tendency to overestimate the probability one assigns to an event once the outcome of that event is known, combined with a denial that such a judgment has been affected by knowledge of the outcome. The article discusses research findings, which demonstrate each of these cognitive processes and show a pattern of results that supports an integrative relationship between them, in the contexts of social cognition and of legal decisionmaking. The article also presents a causal model of decisionmaking in this context, and discusses specific implications of these findings for civil actions to remedy illegal searches. Notes, tables, figures, references