defines to be relevant to their decisions. For example,
jurors use evidence about offenders’ conduct in deter-
mining criminal guilt and civil liability and evidence
about the severity of plaintiffs’ injuries in setting com-
pensation. Indeed, the substantive trial evidence turns
out to be the best predictor of verdicts.EExxttrraalleeggaall EEvviiddeennccee
In some instances, however, jurors may use infor-
mation that has been held to be legally irrelevant.
First, research has demonstrated that jurors sometimes
use information that is related to the case but that
is not part of the legally admissible evidence. For
instance, jurors have difficulty ignoring evidence to
which they are exposed but that is ruled to be inad-
missible by a judge—even when they are explicitly
told to disregard such evidence. In addition, jurors are
influenced by information about a case that that they
obtain through the media—pretrial publicity—but that
is not part of the evidence admitted in the court.
Second, jurors sometimes use evidence that is
appropriately offered for one purpose to inform
another decision for which that evidence is legally
irrelevant. For example, evidence about a criminal
defendant’s prior record is not admissible to establish
guilt, but it may be admitted to discredit the defen-
dant’s testimony. However, jurors have difficulty in
limiting their use of such information. In the same
way, jurors have been shown to conflate their liability
and damages decisions, using evidence that is relevant
to one in making decisions about the other. Similarly,
there is evidence that jurors take into account their
assessment of a plaintiff’s own fault in determining the
level of damage that plaintiff has suffered. Because
these decisions are supposed to be made separately and
then combined by the judge, this can result in a “dou-
ble discounting” of the plaintiff’s damages.
Third, jurors have also been found to rely on pre-
existing cognitive schemas about the law in ways that
may be inconsistent with legal rules. For example,
jurors may bring with them ideas about offenses or
verdict categories that may conflict with the relevant
law. Similarly, in the absence of guidance from the
court about whether or how their decisions should
take into account the possibility that a party is insured
or will incur attorney fees, jurors must rely on their
own notions about the likelihood and nature of any
insurance or fees and about how their decisions
should be informed by these possibilities.Some, but not all, of the difficulties that jurors have
in appropriately dealing with these evidentiary issues
may be related to difficulties that they have in under-
standing jury instructions (see below). In addition,
some studies have shown that jurors are better able to
avoid misusing evidence in some of these ways when
given instructions that explain the rationale underly-
ing the legal rules. For example, jurors are better able
to keep evidence about plaintiff or defendant culpabil-
ity from influencing their damage awards when the
reasons for doing so are explained.HHeeaarrssaayy EEvviiddeennccee
There has also been research examining how jurors
use particular types of evidence. For example, some
studies have examined how jurors assess hearsay
evidence—testimony by a witness relaying what was
said by another person (the “declarant”) that is used to
prove the truth of the matter asserted. Jurors appear to
be able to competently assess hearsay evidence, dis-
tinguishing more reliable hearsay testimony as more
accurate, more helpful to their decisions, and of
higher quality than less reliable hearsay testimony.CCoonnffeessssiioonn aanndd EEyyeewwiittnneessss EEvviiddeennccee
How jurors assess incriminating evidence, such as
confession evidence or eyewitness testimony, has also
been studied. With regard to confession evidence,
there is some evidence that jurors are not influenced
by factors—such as evidence of coercion—that are
associated with the reliability of confessions. There is
similar evidence with respect to eyewitness testimony.
Psychological research has documented a number of
factors that can influence the accuracy of an eyewit-
ness, including the presence of a weapon, the use of a
disguise, or other conditions under which the eyewit-
ness observed the suspect. However, unaided, juror
decisions—such as verdicts, culpability judgments, or
assessments of the accuracy of the eyewitness—may
not be influenced by these factors. In addition, juror
decisions can be insensitive to differences in lineup
procedures. In contrast, there is evidence that jurors
are influenced by the confidence of the testifying eye-
witness, even though confidence is only weakly cor-
related with witness accuracy. Expert testimony about
the influences on eyewitness accuracy (e.g., witness-
ing conditions), however, has been shown to increase
juror sensitivity to such factors and to decrease the402 ———Jury CompetenceJ-Cutler (Encyc)-45463.qxd 11/18/2007 12:43 PM Page 402