Henderson Instructions: Do They Enhance Evidence Evaluation?

ABSTRACT

Mistaken eyewitness identifications are a leading cause of wrongful convictions. Even with procedural safeguards (e.g., attorney argument, cross-examination of witnesses) in place, jurors still have difficulty evaluating the reliability of eyewitness identifications. The purpose of the current study was to test the New Jersey Supreme Court’s assumptions that recently implemented research-based case-specific jury instructions will sensitize jurors to unreliable eyewitness testimony. Four hundred sixty-eight jury-eligible adults watched a trial simulation in which estimator variables, system variables, and jury instruction were manipulated, and subsequently rendered a verdict. The Henderson instructions influenced mock jurors’ perceptions of the eyewitness identification, but these perceptions did not translate to their verdict decisions. Rather than sensitizing jurors, the instructions induced an overall skepticism of eyewitness identification. Taken together, results indicate that the current Henderson instructions should be modified to improve juror sensitivity to various witnessing and identification conditions.

KEYWORDS:

• Eyewitness identification
• eyewitness variables
• judicial instruction
• juror decision making
• system variables

Notes

¹ All manipulated system and estimator variable were mentioned three times: (a) in the opening statements, (b) during the eyewitness or police officer testimony, and (c) in the closing statements. The defense emphasized all variables that were good for the defense, and the prosecution emphasized all variables that were good for the prosecution. In the good system variable–poor estimator variable condition, for instance, the prosecutor mentioned the good system variables in the opening and closing statements and also emphasized them during the police officer’s testimony. The defense attorney mentioned the good estimator variables in his opening and closing statements and also emphasized them during the eyewitness’s testimony. Thus participants were made aware of the positive or negative impact each variable may have had on the identification.

² None of the participants in the pilot study participated in the full study.

³ In the highest conviction condition, there were 6 good witnessing and identification variables present; in the lowest conviction condition, there were 6 poor witnessing and identification variables present.

⁴ Attempted rape cases bring with them unique juror perception issues and gender has been shown to play a significant role in rape trials (see Fischer, 1997; McNamara, Vattano, & Viney, 1993). We thus analyzed whether gender had an impact on verdict, which it did not, p > .05.

⁵ A power analysis (using G*Power) of our most complex hypothesis—an interaction between instruction type, system variables, and estimator variables—suggested a total sample size of 476 to have sufficient power (1-β) = .80 and α = .05 to detect a small-medium sensitivity effect.

⁶ While there were no significant interactions between instruction and system and estimator variables on verdict, results indicated there was a significant interaction between Henderson-before instructions and estimator variables on jurors’ ratings of the impact of the weapon on the likelihood of an accurate identification. When estimators were poor, jurors who heard the Henderson-before instructions rated the weapon as having decreased identification accuracy significantly more so than those who heard no eyewitness instruction (p < .01). When estimators were good, there was no difference in jurors’ ratings of the impact of the weapon as a function of instruction type (all ps >.65). However, given the number of tests included in the analysis, we suspect this interaction may be the result of Type I error.

⁷ Eyewitness identification instructions developed after decision in United States v. Telfaire, 1972.

⁸ Note these instructions are for the conditions in which the quality of both system and estimator variables are poor and are thus the most comprehensive version of the instructions given to participants. According to the Court in Henderson, the instructions should include all variables that are relevant to a specific case and should appear in this order. Thus, in addition to the variables we manipulated, we included as constants all variables that may have had an effect on the identification (e.g., stress).