Dateline: July, 2008, Issue 1
How does expert testimony about eyewitness fallibility affect verdicts?
Eyewitness testimony is fallible. Mistaken eyewitness testimony is the leading cause of false convictions, accounting for more criminal convictions of innocent people than all other causes combined (see, for review, Wells et al., 1998).
Lawyers' cross-examination skills often cannot overcome jurors' belief in an eyewitness. When experienced attorneys cross-examine eyewitnesses, jurors still often perceive the testimony of accurate and inaccurate eyewitnesses as being equally credible (Lindsay et al., 1989). When an eyewitness is discredited through cross-examination, the eyewitness is still more persuasive on verdicts than when no eyewitness testifies at all (Whitley, 1987).
Wells and colleagues (1980) found that having a psychologist testify that eyewitness confidence had nothing to do with identification accuracy increased jurors' doubt in the eyewitness testimony.
Loftus (1980) found that including testimony from a psychologist that explained the fallibility of eyewitness testimony reduced conviction rates from 47% to 35% in an assault case, and from 68% to 43% in a murder case.
Expert testimony sensitizes jurors to the fallibility of eyewitness identifications, though it does not entirely eliminate problems jurors have with evaluating eyewitness testimony.
Source Wells, G. L., Small, M., Penrod, S., Malpass, R. S., Fulero, S. M., & Brimacombe, C. A. E. (1998). Eyewitness identification procedures: Recommendations for lineups and photospreads. Law and Human Behavior, 22, pp. 1-39.
Source Lindsay, R. C., Wells, G. L., & O'Connor, F. J. (1989). Mock juror belief of accurate and inaccurate eyewitnesses: A replication and extension. Law and Human Behavior, 13, pp. 333-339.
Source Whitley, B. E. (1987). The effects of discredited eyewitness testimony: A meta-analysis. Journal of Social Psychology, 127, pp. 209-214.
Source Wells, G. L., Lindsay, R. C., & Tousignant, J. P. (1980). Effects of expert psychological advice on human performance in judging the validity of eyewitness testimony. Journal of Applied Social Psychology, 15, pp. 758-772.
Source Loftus, E. F. (1980). The impact of expert psychological testimony on the unreliability of eyewitness identification. Journal of Applied Psychology, 65, pp. 9-15.