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When are people persuaded by DNA match statistics?
1McCombs School of Business and School of Law, University of Texas at Austin, CBA 5.202, Austin, Texas 78712-1175, USA. koehler@mail.utexas.edu
Law and Human Behavior
|November 2, 2001
Summary
How statistical DNA evidence is presented significantly impacts its persuasiveness in legal settings. Framing DNA match statistics as individual probabilities, rather than reference group frequencies, enhances their perceived strength.
Area of Science:
- Forensic Science
- Cognitive Psychology
- Legal Decision-Making
Background:
- The presentation of statistical DNA evidence influences legal decision-makers' perceptions.
- Prior research indicates that presentation framing can alter the perceived certainty of evidence.
Purpose of the Study:
- To investigate how different presentation formats of statistical DNA evidence affect its persuasiveness.
- To test exemplar cueing theory regarding the cognitive availability of coincidental matches.
Main Methods:
- Three experiments were conducted to examine the impact of presentation framing on DNA evidence persuasiveness.
- Statistical DNA match evidence was presented using probabilities targeting individual suspects versus frequencies targeting reference groups.
Main Results:
- Probability-based, individual-targeted DNA evidence was more persuasive than equivalent frequency-based, group-targeted evidence.
- The effect of presentation framing was less pronounced at extremely low incidence rates.
- Exemplar cueing theory explains these effects based on the cognitive availability of coincidental matches.
Conclusions:
- The cognitive availability of coincidental matches influences the perceived probative value of DNA evidence.
- Strategic presentation of DNA evidence, emphasizing individual probabilities, can enhance its persuasive impact in legal contexts.
- Understanding presentation effects is crucial for the effective use of statistical evidence in trials.