A Model of Criminal Justice Discretion

Criminal prosecutors wield tremendous power in the American legal system. However, their ability to direct prosecution against criminal suspects relies on coordination with the police who investigate crimes and make arrests. That relationship has become more prominent with the rise of reform prosecutors who propose to shift traditional law-enforcement priorities. I develop a model of police–prosecutor interaction built around an informational asymmetry that past research on prosecution has not analyzed. Police hold private information about the culpability of an arrested suspect, but they also have their own preferences over how that suspect is charged. I ask how a prosecutor’s interest in leniency affects whether police can credibly communicate what they know. Two findings stand out. First, alignment between police and prosecutors is observationally equivalent across very different underlying relationships. Apparent cooperation can reflect either credible communication or its absence, so the alignment we observe cannot by itself reveal whether police information is reaching prosecutors. Second, the court’s willingness to acquit an over-charged suspect, ordinarily treated as waste, is what makes truthful communication possible, because the prospect of acquittal disciplines the allegations police bring. These results caution against reading cooperation between police and prosecutors as evidence of well-functioning justice, and they bear on how we evaluate criminal justice reform.