Evaluating Identification Evidence from Multiple Eyewitnesses


Requests for reprints should be sent to Glenn S. Sanders, Department of Psychology, SUNY/Albany, 1400 Washington Ave., Albany, NY 12222.


When two or more eyewitnesses provide identification evidence in a given investigation, their testimony will be characterized either by unanimity or by contradictions. In the present research, nominal groups of several sizes were constructed from the distributions of individual responses in a variety of previous studies. It was found that both unanimity and contradictions could be expected to occur with considerable frequency. When unanimity occurred, the unanimous response was very likely to be accurate, particularly in large groups. When contradictions occurred, the most common, or modal, response was most probably accurate, particularly when four or more witnesses endorsed the modal position. These and several subsidiary findings resulted largely from the fact that individual errors were randomly distributed across many different incorrect response options. Consequently, even when eyewitnesses were generally inaccurate, the correct option was still chosen more frequently than any single incorrect option. Distinctions between the implications of individual vs. multiple eyewitness testimony were discussed.