The Influence of Expert Witnesses on the Jury

    We see and hear about experts being used all the time and maybe even use them ourselves, but how influential are they really? Are they really as influential as we think? 

What the Studies Have Found

    There are many factors to consider when looking at what influences a juries decision, but what do we find when we look specifically at expert witnesses? There were 3 studies that were done that looked at the influence that expert testimony has on juror's decisions and behaviors. Hosch.The studies focused on the influence that psychology experts have regarding the accuracy of eyewitness identification. They compared the influences in the presence of expert testimony versus the absence of expert testimony in the following situations: in a courtroom versus in a laboratory, violent crimes versus nonviolent crimes, and accurate versus inaccurate eyewitnesses. Each of the studies found that expert testimony had a significant affect on the jurors decisions. 

    They found that when the jurors heard expert testimony, the jurors analyzed and reviewed the evidence more and were less likely to believe in the accuracy of the eyewitness testimony. The studies also found that though expert testimony has some influence, it is not very much in regards to the variance of verdicts - it only accounts for about 3%. But they tend to have a stronger influence on a jury's deliberation time. The studies found that the presence or absence of expert testimony accounts for about 31% of the difference in deliberation times. Experts make people more critical of the evidence that is before them and thus leads to longer and further deliberation among the jurors. It was further found the presence and/or absence of expert testimony had  17% affect on their belief or lack of belief of the eyewitness testimony that was presented to them. 

Conclusion: Key Take Aways

    Based on these studies we can conclude that expert testimony will influence the behaviors and beliefs of the jurors. We can conclude that this is true across all kinds of cases no matter how the information is presented to them and how general or specific the information is. We also can expect that the expert testimony will affect the jurors no matter the jurors own backgrounds, demographics, or personality characteristics. Although the effect that expert testimony has on the final verdict is small (which is reasonable considering there are a lot of factors that affect the final verdict), the testimony will effect the jurors analysis of the information and evidence that are presented to them. Expert testimony will increase the jurors scrutiny of not only the evidence but also the lay witness testimony that is presented to them as well. Something as simple as eyewitness testimony may not be as simple as eyewitness testimony after the jury has heard from expert witnesses. Thus, expert testimony has a large impact on how the information is analyzed and considered by the jury and may promote a more thorough deliberation and a more rational outcome. Expert testimony appears to be the means to a more just end.

    Although these studies only consider a very small area of expert testimony, I think that we can still conclude that expert testimony really is as influential as we think.