Bargaining in the Shadow of the Trial

Bargaining in the Shadow of the Trial: Introductory Text Exploring the Reach of Evidence Outside the Jury Box

The National Institute of Justice

Co-PI: Shawn Bushway

Project Researchers: Robert Norris and Rose Bellandi

Abstract
There is overwhelming consensus that “strength of evidence” (SOE) drives guilty pleas. But, what is “strength of the evidence”? Despite the clear consensus about its import in legal decision-making, it has not been well conceptualized or measured. In the proposed study, our objectives are to 1) operationally define “strength of the evidence,” and 2) once defined, examine its role and the role of extralegal factors, in plea negotiations.

Theorists contend that pleas occur “in the shadow of a trial,” meaning that plea decision-making is premised on the perceived probable outcome of a trial. However, the decision to plea is not directly analogous to the jury decision because parties to a plea are bargaining simultaneously about conviction and sentence length. We study the role of evidence in pleas by estimating a plea bargain analog to the probability of conviction at trial. In this way, we can directly test whether evidence plays a similar role in the plea bargaining process as it does at trial. Such a test will not only provide important information about the value of evidence in the predominant form of conviction (pleas) in the U.S. criminal justice system, but it will also provide a direct test of the predominant “shadow of trial” theory of plea bargaining. We conduct two phases of research in which we replicate and extend a watershed NIJ-funded study from the 1970s (Miller, McDonald, & Cramer, 1978).

In Phase I, we manipulate the presence and combination of three evidence forms (eyewitness, confession, and DNA), and the prior criminal history of the defendant in hypothetical case scenarios administered to nationally representative samples of judges, prosecutors, and defense attorneys. Using a sophisticated and user-friendly web-based survey, we assess the relative importance of evidence, as well as extra-legal factors in the perceived probability of conviction and willingness to plea.

In Phase II, we partner with three county DA offices to code the evidentiary and non-evidentiary factors in actual criminal case files. We determine the influence of these factors on the probability of a conviction estimated from the value of plea bargains using a methodology pioneered by Piehl and Bushway (2007). We then use these values to estimate the probability of conviction at trial, determining the role of evidence and extralegal factors in this estimated probability. In both study phases, we will use our estimates to create a measure of strength of evidence that reflects the ability of various kinds of evidence to drive convictions.

Findings from the proposed study have many implications for U.S. criminal justice practices. In a system in which only three percent of convictions are the result of jury trials, information on how judges and attorneys make plea decisions will be extremely valuable. In both study phases, we will be able to determine how evidence quantity and quality influences the probability of conviction and the value of pleas. Our findings can also yield insight into the possible methods by which plea bargaining can become more structured. For example, if we find that the value of the plea is largely unexplained by SOE, and more to the point, is correlated with extra-legal factors, researchers and policymakers interested in developing a more consistent and fair legal system should focus attention on investigating this relatively unstructured source of sentencing disparity.