JUDICIAL NOTEBOOK

Courts continue to exclude expert evidence on witness credibility

By Michael Mishlove, JD, Foley & Lardner
and Larry Heuer, PhD, Barnard College

Two appellate decisions affirming the exclusion of psychologists' expert testimony in criminal proceedings reveal that judges continue to be skeptical about the utility of expert testimony concerning eyewitness reliability. Both decisions appear to disregard the compelling body of empirical evidence about the benefits of expert assistance.

Background on the cases

In United States v. Hall, 165 F.3d 1095 (7th Cir. 1999), the U.S. Court of Appeals for the Seventh Circuit affirmed the kidnapping conviction of Larry Hall. His conviction was aided by the testimony of four eyewitnesses who placed him at the crime scene. The trial court excluded testimony by the defense's expert who would have addressed the weak correlation between witness confidence and reliability, as well as various threats to reliability of eyewitness identification.

Under the applicable evidentiary standards, a trial judge faced with such testimony must consider whether it is based on scientific knowledge and whether it will assist the jury in determining a fact at issue. In Hall, the government argued that the testimony would not assist the jury and the trial judge agreed.

Affirming the trial court's exclusion of the expert testimony, the Court explained that "expert testimony regarding the potential hazards of eyewitness identification--regardless of its reliability--will not aid the jury because it addresses an issue of which the jury already generally is aware and it will not contribute to their understanding of the particular factual issues posed." Second, the Court voiced confidence that traditional cross-examination techniques will adequately convey to the jury the weight to be afforded any eyewitness testimony. Finally, the Court opined that appropriate instructions to the jury--advising the jury to consider factors influencing eyewitness identification--in conjunction with vigorous cross-examination should adequately focus the jury on the issue of eyewitness identification and render the jury "fully able to assess the ability of the eyewitnesses to perceive and remember."

Similarly, the Connecticut Supreme Court recently found no error in the exclusion of expert testimony on eyewitness reliability, and affirmed Charles McClendon's murder and robbery convictions. In the case State v. McClendon 248 Conn. 572 (Conn. 1999), the trial judge excluded the expert testimony because it was within the general knowledge of the jurors. The Connecticut Supreme Court agreed: "These general principles should come as no surprise to the average juror. It is common knowledge that eyewitnesses may make mistakes and may forget what they have seen." Like the Hall court, the Connecticut Supreme Court invoked the notion that the "weaknesses of identifications can be explored on cross-examination and during counsel's final arguments to the jury."

The majority decisions in Hall and McClendon provoked thoughtful and persuasive minority views, which drew on social science scholarship. In McClendon, Justice Berdon, dissenting, drew on the work of psychologist Elizabeth Loftus to emphasize the overwhelmingly influential impact of eyewitness testimony on jury decision-making, and the diminished accuracy of cross-racial identification (which McClendon involved). Justice Berdon rejected the contention that the substance of the expert testimony is within the ken of lay understanding: "The empirical evidence conclusively demonstrates that this court's faith in the acumen of laypersons [is] misplaced.[I]t is clear (1) that the reliability of eyewitness identifications cannot be adequately questioned through either cross-examination or closing argument and (2) that jurors are not capable of understanding apparent indicia of reliability without the aid of expert testimony."

In Hall, Judge Easterbrook voiced similar themes: "Properly conducted social science research often shows that commonly held beliefs are in error. Jurors who think they understand how memory works may be mistaken, and if these mistakes influence their evaluation of testimony, then they may convict innocent persons. That a subject is within everyday experience does not mean that jurors know it correctly. The lessons of social science thus may be especially valuable when jurors are sure they understand something, for these beliefs may be hard for lawyers to overcome with mere argument and assertion."

Implications for psychologists

In both Hall and McClendon, the minority view appears to appreciate the increasingly compelling empirical evidence leading Brian Cutler and Steven Penrod (1995) to conclude that (1) jurors overestimate eyewitness identification accuracy and are insufficiently sensitive to the viewing conditions known to predict accuracy; (2) traditional safeguards such as cross-examination and judges' instructions are ineffective; and (3) "[e]xpert psychological testimony shows a greater promise as a safeguard against mistaken identifications and erroneous convictions."

Recently, Gary Wells et al. (1999) reported that in a sample of 40 convicts who were subsequently exonerated through DNA analyses, 90 percent of the trials resulting in the convictions involved eyewitness-identification evidence in which the defendant was falsely identified. The paper alludes to "increasing evidence that false eyewitness identification is the primary cause of the conviction of innocent people."

Such failures, and the prospect for minimizing them through the introduction of expert evidence on eyewitness reliability, serve as a potent reminder of the need for a sustained effort by the research community to educate the courts about the relevant social science evidence.



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