Encyclopedia of Psychology and Law

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Wirth-Cauchon, J. (2001). Women and borderline personality

disorder.New Brunswick, NJ: Rutgers University Press.

PLEABARGAINING

Plea bargaining is a process in a criminal case whereby

the defendant agrees with the prosecutor to plead guilty

(or no contest) in exchange for a reduction in charges

or a reduction of sentence. By pleading guilty, the

defendant gives up the right to go to trial. Contrary to

the widespread belief that criminal cases are usually

resolved through jury trials, in reality as many as 95%

of criminal cases are handled by plea bargaining. This

bargaining process has been viewed by some as a ratio-

nal one in which the participants take into account both

the probability of conviction and the likely sentence if

the defendant were to be found guilty at trial; the par-

ticipants arrive at a bargain that is fair to both sides.

Critics of plea bargaining have focused on the flaws in

the system that distort the process, such as heavy case

loads, which cause prosecutors or public defenders to

favor plea bargains over trials in almost all circum-

stances, regardless of the merits of the case. Additional

causes for imperfect bargains involve psychological

influences that lead to poor decision making. In spite

of its importance to the criminal justice system, only a

limited amount of research exists on the topic of plea

bargaining.

Decision Theory Approach

Decision theory’s concept of value maximization has

been used to explain the plea bargaining decisions

made by the prosecution and the defense. According

to this model, both sides consider both the probability

of conviction at trial and the severity of sentence given

a jury finding of guilt; multiplying the probability of

conviction by the sentence gives one the expected

value of going to trial. The desirability of a plea bar-

gain offer is based on its comparison with the

expected value of going to trial. For example, consider

a case in which, based on the evidence, there was a

50% chance that the jury would find the defendant

guilty and, if found guilty, the sentence would be 10

years of imprisonment. The expected value of going

to trial would be 5 years (.5 × 10 years). A plea

bargain agreement of anything less than 5 years would

be a good bargain for the defense, whereas anything

over 5 years would be a good bargain for the prosecu-

tion. A bargain that would be acceptable to both sides

would be close to 5 years. In a perfectly rational world,

taking the case to trial and plea bargaining would have

the same value, and one might expect the participants

to be somewhat indifferent between trial and plea

bargain.

Research has shown that plea bargaining partici-

pants do, in fact, consider the probability of convic-

tion and the severity of the sentence. Plea bargaining

decisions by prosecutors and the defense have been

found to be influenced by both variables; however,

these two variables alone do not suffice to explain the

plea bargaining decisions. Other factors are involved.

Self-Interests of the Bargainers

Certain influences on plea bargaining that are exoge-

nous to the merits of the case affect all the major

participants—prosecutor, defense attorney/defendant,

and judge. Each of these participants has self-interests

outside the merits of the case that might distort the

plea bargaining process.

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It has been argued, and there is some empirical

support for the idea, that prosecutors favor resolving

cases by plea bargaining as opposed to trials. Trials

involve a much greater commitment of the prosecu-

tor’s time and resources. It has been argued that

prosecutors do not have the resources to take any

more than a small proportion of their cases to trial;

thus, by necessity they must use the more efficient

plea bargain to resolve most cases. However, some

research has shown that even in districts where the

case loads are light, plea bargaining rates remain at

the same high level. Even when the case load is low,

a prosecutor might prefer not to devote all the time

and energy required for a jury trial, particularly

given the way prosecutorial performance is evalu-

ated. Prosecutors’ reputations are based on their con-

viction rates. A case in which a defendant pleads

guilty as a result of a plea bargain counts as a con-

viction for the prosecutor. Thus, for the prosecutor,

even if a plea-bargained sentence is under the deci-

sion theory expected value, from a self-interest

standpoint, it is still desirable because it counts as

a conviction.

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