Signaling and Plea Bargaining's Innocence Problem

I. IntroductionPlea bargaining has an innocence problem. The dominant theoretical model of plea bargaining - so-called "trial shadow theory" - predicts that, once charged, innocent and guilty persons alike almost always act rationally by pleading guilty rather than contesting guilt at trial.1 Indeed, it predicts that every case able to withstand minimal pretrial scrutiny should be resolved (assuming the parties are adequately informed about the evidence and act rationally) with a negotiated plea bargain.2 By all accounts, those predictions are not far off the mark. The latest data available indicates that approximately 95% of all adjudicated felony criminal charges are disposed with through guilty pleas.3 When more than forty-seven out of every fifty dispositions are guilty pleas, it is safe to say the theory is on to something.Plea bargaining's critics have responded to the avalanche of guilty pleas with a wide range of proposed reforms. Some have advocated total abolition of plea bargaining;4 others have urged shifting resources to early screening to prevent weak cases from being prosecuted.5 Still others have called for more liberal discovery requirements to increase the amount of information available to defendants at the time they enter guilty pleas.6 Although there are merits to all these suggestions, none do much to address the innocence problem- at least not without imposing costs upon society (in the form of making it harder to convict the guilty) that society seems ill-prepared to accept. In fact, some of these reforms - abolition and enhanced pre-plea discovery in particular - might well make innocent defendants worse off rather than better, or at least more likely to enter false guilty pleas.The economic model of plea bargaining highlights the central dynamic driving the innocence problem: As long as plea prices are determined by trial shadows, anything that fails to cast a trial shadow is irrelevant to plea prices. But information that is irrelevant to trial outcomes might not be irrelevant to other important issues that bear upon just outcomes. Take, for instance, a defendant's honest but unverifiable belief that she is factually innocent of the crime charged.7 Although seemingly a highly salient piece of information, such private information cannot affect plea prices if the defendant has no way to communicate the information to the prosecutor or a jury. As a result, defendants who know they are innocent would appear to do no better in plea bargaining than defendants who know they are guilty.8 In game theory terms, pleading guilty pursuant to a utility-maximizing bargain is a "dominant strategy" for guilty and innocent defendants alike, irrespective of the content of private information.Plea bargaining's dominance as a strategy depends, of course, on the assumptions that one makes about the payoff structure and rules of the game. Under standard assumptions, private information about guilt and innocence is irrelevant to plea bargaining outcomes. Under other payoff and rule structures, however, private information can be made relevant through what economists refer to as "signaling."9 This Article discusses one such payoff and rule structure, which I refer to as a "subwager," that might permit incorporation of private information into plea pricing to improve the accuracy of the pricing system. In other words, under certain circumstances subwagers might increase sentence differentials between defendants who know they are innocent and those who know they are guilty.Part II describes the innocence problem in greater detail and demonstrates why abolition, stronger prosecutorial charge screening, and enhanced discovery all fail to resolve it. Part III then considers the innocence problem as a signaling defect. Innocent defendants have private information that is relevant but not verifiable. Because they cannot reliably signal their innocence in a manner prosecutors can trust, that private information is effectively lost. …