Arizona Jury Research

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DOES THE TIMING OF EXPERT TESTIMONY IMPACT VERDICTS?

By Jan Mills Spaeth, Ph.D., Advanced Jury Research

This article was published in THE WRIT, the official publication of the Pima County Bar Association, in July, 2004. This is a brief synopsis of a research study.

Statistically, the majority of eyewitness are called by the prosecution as incriminating evidence. Expert testimony regarding the reliability of eyewitness identification is usually presented by the defense after the prosecution's case has rested, toward the end of trials.

Does the fact that defense experts on eyewitness credibility testify after the eyewitnesses put the defense at a disadvantage? In other words, does the prosecution get the advantage because of the "primacy effect" when their witnesses go first? Or, does the defense benefit from the "recency effect" when their experts testify last?

This is an interesting question because eyewitness identification has a major impact on jurors, often more so than it should. For example, as of the year 2000, of the 62 cases in which individuals convicted and imprisoned for felonies were later exonerated by DNA evidence, 52 of these cases involved mistaken eyewitness identification (eight of these involved death sentences).

As the strength of the prosecution case increases with physical or incriminating evidence, the less impact eyewitness testimony has on verdicts, and thus the less impact expert testimony regarding eyewitnesses has on verdicts. Eyewitness testimony is often the primary evidence against defendants, however, and jurors tend to over-believe eyewitnesses.

As a result, it is important to determine whether experts testifying after eyewitnesses have much impact in terms of “remedying” juror bias in favor of eyewitness testimony. To what extent are these experts successful in educating jurors about memory, and its proneness to error?

There are certainly advantages for the prosecution in having their eyewitnesses testify early in the trial. Primarily, jurors will use this testimony to develop a crime theme, and will be most ______American Society of Trial Consultants American Psychological Association American College of Forensic Examiners P.O. Box 91410, Tucson, AZ 85752-1410 (520) 297-4131 Fax (520) 797-4213, [email protected] Does The Timing Of Expert Testimony Affect Verdicts?, Jan Mills Spaeth, Page 2

susceptible to evidence and arguments that support this theme. Jurors are also prone to interpreting later testimony and evidence according to the theories they develop early in the trial. It can often be an "uphill battle" for the defense to alter the mindset of jurors established by prior evidence and testimony.

On the other hand, there are distinct advantages to presenting expert testimony toward the end of trials. First, because of the "recency effect", the testimony may be more easily and spontaneously recalled in deliberations. Second, this testimony is often subject to fewer compelling counterarguments, especially since this testimony cannot be followed by an opposing expert.

The authors of a recent study regarding the timing of expert testimony obtained some interesting results in their research. (See “Timing of eyewitness expert testimony, jurors need for cognition, and case strength as determinants of trials verdicts,” by Leippe, Eisenstadt, Rauch & Seib, Journal of Applied Psychology, June, 2004.)

These researchers found that the mere introduction of expert testimony regarding eyewitnesses, following their testimony, caused heightened skepticism about this testimony. Many jurors began worrying about whether they initially over-believed the eyewitnesses. This was especially true when the experts introduced new, case specific information as opposed to generalized testimony.

Expert testimony discrediting eyewitnesses had the most impact when it was later in the trial, after the eyewitnesses had testified, and followed by judges’ instructions on judging the credibility of eyewitnesses. Jury instructions regarding eyewitness credibility, when given fairly close to the expert testimony, tended to enhance the credibility of the experts. The judges’ instructions may have been seen as allowing or authorizing skepticism toward eyewitnesses by the jurors.

As a result, instructions by judges shortly after the testimony of experts encouraged jurors to consider the expert testimony when determining the credibility of eyewitnesses, helped to offset pre-dispositions in terms of over-believing the eyewitnesses.

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