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Insights: Battling to a Draw


Battling to a Draw:

Defense Expert Rebuttal Can Neutralize Prosecution Fingerprint Evidence


While all forensic science disciplines pose some risk of error, the public typically believes that testimony from fingerprint experts is infallible. By employing rebuttal experts who can educate jurors about the risk of errors or provide opposing evidence, courts can counter this tendency. CSAFE funded researchers conducted a survey to study the effect of rebuttal experts on jurors’ perceptions.

Lead Researchers

Gregory Mitchell
Brandon L. Garrett


Applied Cognitive Psychology

Publication Date

4 April 2021

Publication Number




Determine if a rebuttal expert’s  testimony can affect jurors’ beliefs in the reliability of fingerprint evidence.


Examine the responses of jurors with different levels of concern about false acquittals versus false convictions.

The Study


Participants completed a survey which included questions regarding their concerns about false convictions or false acquittals.

The participants were then assigned to random mock trial conditions:

Control condition with no fingerprint evidence

Fingerprint expert testimony with no rebuttal

A methodological rebuttal: the expert focuses on the subjective nature of fingerprint analysis as a whole

An “inconclusive” rebuttal: the expert opines their own comparison was inconclusive due to the poor quality of the evidence

An “exclusion” rebuttal: the expert states that their own comparison shows the defendant could not have been the source of the fingerprints


Trial Condition

% Voting for Conviction

Trial Error Aversions

Mean Likelihood D Committed Robbery

Focus on the future


While exclusion and inconclusive rebuttals provided the best results for the defense, the methodological rebuttal still significantly impacted the jurors’ views on fingerprint evidence.

Traditional cross-examination seems to have mixed results with forensic experts. This implies that a rebuttal testimony can be more effective and reliable, while producing long-term changes in jurors’ attitudes.

While a rebuttal expert’s testimony can be powerful, much of that power depends on the individual jurors’ personal aversions to trial errors. This could be an important consideration for jury selection in the future.

Check out these resources for additional research on forensic evidence and juries: