Encyclopedia of Psychology and Law

Psychological Influences

In addition to the various ways in which the self-

interest of the various actors might distort plea bar-

gaining decisions, a number of psychological

influences have been found to distort decision mak-

ing in any number of situations. For example, how

decision alternatives are framed has been found to

have a major impact on people’s willingness to take

risks. It has often been shown that when the decision

alternatives are framed in terms of losses, the deci-

sion makers become more averse to risk; in contrast,

when the alternatives are framed in terms of gains,

individuals are more willing to take chances.

Consider the case in which a plea bargain of 5 years

is being evaluated in light of the probability of con-

viction at trial of 50%, with a sentence of 10 years.

Defendant A is told that if he goes to trial, there is a

50% chance that he will lose an additional 5 years of

his life above the plea bargain. In contrast, defendant

B is told that if he were to go to trial, there is a 50%

chance that he would gain an additional 5 years of his

life as compared with the plea bargain. Although both

defendants are facing the same situation, Defendant

A will plea bargain to avoid the loss, and Defendant

B will take the risk of going to trial for the potential

gain. Framing can influence defense attorneys and

prosecutors as well as defendants.

When people attempt to form judgments in

ambiguous situations, they will often start from some

anchor point and then make adjustments. If a prose-

cutor makes an unreasonable initial plea bargain offer

of 20 years, which is summarily rejected, it still acts

as an anchor against which subsequent bargains are

evaluated. A subsequent offer of 10 years that would

have been rejected had it been the first offer now

becomes desirable when compared with the 20-year

anchor. As with framing, anchoring effects influ-

ence prosecutors and defense attorneys as well as

defendants.

Various types of attributional biases also play a part

in plea bargaining. For example, one type of attribu-

tion bias that protects us from feelings of vulnerabil-

ity is unrealistic optimism. Individuals tend to believe

that bad things happen to other people but not to them.

It would be quite natural for the defendant to believe

that if the case were to go to trial, there would be

a verdict of not guilty; this bias would be one of the

factors causing a defendant to prefer a trial to a plea

bargain.

Limitations of Research

on Plea Bargaining

It should be noted that our knowledge about plea bar-

gaining is based on an extremely small body of

research. In contrast to other topics in psychology and

law, such as juror decision making or eyewitness testi-

mony, for which there are literally hundreds of studies,

only a handful of studies exist on plea bargaining. It is

particularly surprising that the topic of juror decision

making has been so heavily researched, since only 5%

to 10% of cases are resolved by jury. In addition to the

limited number of studies on plea bargaining, much of

the research that has been conducted has been poorly

controlled. Much of our understanding of plea bargain-

ing is based on interviews or observations of individu-

als who were available to the researcher as opposed to

individuals selected through systematic sampling tech-

niques.Most of the support for psychological influences

is based on generalizations from other bargaining situ-

ations rather than on plea bargaining situations them-

selves. Given the centrality of plea bargaining to

the criminal justice system, it is imperative that we

increase both the quality and the quantity of research

on how this process works.

Hunter A. McAllister

See alsoAlternative Dispute Resolution; Legal Negotiation;

Litigation Stress

Further Readings

Alschuler, A. W. (1975). The defense attorney’s role in plea

bargaining. Yale Law Journal, 84,1179–1314.

Bibas, S. (2004). Plea bargaining outside the shadow of trial.

Harvard Law Review, 117,2463–2547.

Fisher, G. (2003). Plea bargaining’s triumph: A history of

plea bargaining in America.Stanford, CA: Stanford

University Press.

Heumann, M. (1979). Plea bargaining: The experience of

prosecutors, judges, and defense attorneys.Chicago:

University of Chicago Press.

POLICE ASEYEWITNESSES

Criminal cases often hinge on the testimony of eyewit-

nesses; sometimes those eyewitnesses are police offi-

cers. Police eyewitnesses perform the same tasks as

Police as Eyewitnesses——— 561

P-Cutler (Encyc)-45463.qxd 11/18/2007 12:43 PM Page 561