I recently read Greg Mitchell and Brandon Garrett’s The impact of proficiency testing information and error aversions on the weight given to fingerprint evidence.
Mitchell and Garrett performed a behavioural study, informing mock jurors of the the results of a fingerprint examiner’s proficiency tests. They also manipulated the types of errors the proficiency tests revealed (if any): false positives and false negatives. They wanted to see if this information would affect the weight given to the evidence and the mock jurors’ perception of the strength of the case.
Mitchell and Garrett found that their participants were sensitive to proficiency information. In particular, when proficiency was higher, participants reported it was more likely the accused in the mock trial left the prints. There wasn’t, however, a significant difference between perfect and high proficiency, and high and medium. I wonder if these are the most likely levels of proficiency for most examiners, and thus whether in practice these results will matter. Still, it’s very good to know that proficiency information has some effect.
The participants did not seem to distinguish between types of error, suggesting that it perhaps became too technical for them at that point and they needed more direction.
Finally, I wish that Mitchell and Garrett had included a DV about whether the juror would vote to convict beyond a reasonable doubt. I’d be curious to see if just showing the examiner had 98% proficiency could drop votes from convict to not guilty.