ANALYSIS OF SCIENTIFIC RESEARCH ON EYEWITNESS IDENTIFICATION January 2018 Patricia A. Riley U.S. Attorney’s Office, DC Table of Contents RESEARCH DOES NOT PROVIDE A FIRM FOUNDATION FOR JURY INSTRUCTIONS OF THE TYPE ADOPTED BY SOME COURTS OR, IN SOME INSTANCES, FOR EXPERT TESTIMONY ...................................................... 6 RESEARCH DOES NOT PROVIDE A FIRM FOUNDATION FOR JURY INSTRUCTIONS OF THE TYPE ADOPTED BY SOME COURTS AND, IN SOME INSTANCES, FOR EXPERT TESTIMONY .................................................... 8 Introduction ............................................................................................................................................. 8 Courts should not comment on the evidence or take judicial notice of contested facts ................... 11 Jury Instructions based on flawed or outdated research should not be given .................................. 12 AN OVERVIEW OF THE RESEARCH ON EYEWITNESS IDENTIFICATION OF STRANGERS, NEW AND OLD .... 16 Important Points .................................................................................................................................... 16 System Variables .................................................................................................................................... 16 Simultaneous versus sequential presentation ................................................................................... 16 Double blind, blind, blinded administration (unless impracticable .................................................... 17 Witness instructions ........................................................................................................................... 18 Estimator Variables ................................................................................................................................ 20 Confidence and accuracy ................................................................................................................... 20 Speed of Identification ....................................................................................................................... 21 Stress .................................................................................................................................................. 21 Weapon focus effect (WFE) ................................................................................................................ 23 Cross-race ........................................................................................................................................... 24 Opportunity to view ........................................................................................................................... 26 Exposure time/Retention interval ...................................................................................................... 27 Intoxication ........................................................................................................................................ 28 Descriptions ........................................................................................................................................ 28 Disguise .............................................................................................................................................. 29 CONFIDENCE AND ACCURACY .................................................................................................................... 30 CONFIDENCE AND ACCURACY .................................................................................................................... 31 Research as Summarized in the Henderson Jury Instruction ................................................................. 31 Analysis .................................................................................................................................................. 31 DC 2/1/2018 2 The Confidence-Accuracy Characteristic establishes that highly confident suspect identifications are highly accurate and moderately confident witnesses are only slightly less so. ................................. 32 Historical reasons for misunderstanding the strength of the relationship between confidence and accuracy. ............................................................................................................................................ 35 Archival and field studies demonstrate that highly confident witnesses are highly accurate. .......... 41 The results of all identification procedures should be fully disclosed to the jury. ............................. 41 Conclusion .............................................................................................................................................. 42 STRESS ............................................................................................................ 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STRESS ........................................................................................................................................................ 44 Research as Summarized in the Henderson Instruction ......................................................................... 44 Analysis .................................................................................................................................................. 44 Stress does not increase false identifications. ................................................................................... 44 In the Morgan study, high stress reduced the percentage of false identifications. ........................... 45 In the Deffenbacher meta-analysis, one study was responsible for most of the difference in effect sizes. ................................................................................................................................................... 45 There is no uniform standard as to what constitutes “a high level of stress” and no way to measure it. ........................................................................................................................................................ 47 Laboratory experiments often use stressors that are external to the event and may serve as distractors. ......................................................................................................................................... 48 Memory is better for central details than peripheral ones. ............................................................... 49 The same event affects different people differently. ......................................................................... 50 Some people do better under high stress; stress does not increase – and may in fact reduce – the chance that an innocent suspect will be chosen. ............................................................................... 51 Highly confident witnesses are highly accurate. ................................................................................ 51 Conclusion .............................................................................................................................................. 52 WEAPON FOCUS EFFECT ............................................................................................................................ 53 WEAPON FOCUS EFFECT ............................................................................................................................ 54 Research as Summarized in the Henderson Instruction ......................................................................... 54 Analysis .................................................................................................................................................. 54 There is insufficient evidence that the presence of a weapon increases false identifications for expert testimony or jury instructions. ................................................................................................ 54 If the presence of a weapon has any effect in the real world, it reduces both true and false identifications. .................................................................................................................................... 55 DC 2/1/2018 3 Highly confident witnesses are highly accurate even when a weapon is clearly visible. ................... 56 If a witness was not distracted by the presence of a weapon, then there could be no “weapon focus effect.” ............................................................................................................................................... 57 Laboratory research does not replicate real-life conditions or circumstances. ................................. 57 The presence of a weapon affects feature accuracy much more than identification accuracy. ........ 58 Average accuracy is meaningless in the courtroom. .......................................................................... 59 In the laboratory, the weapon focus effect on identification accuracy is small. ................................ 59 There is conflicting data in laboratory studies about how the length of exposure affects the weapon focus effect. ........................................................................................................................................ 60 The weapon focus effect may be limited by an eyewitness’s proximity to a perpetrator. ................ 61 The weapon focus effect may depend on the individual qualities of the eyewitnesses. ................... 61 Laboratory research on the weapon focus effect is evolving. ...........................................................