Thursday, March 7, 2013

Research Byte: When Forensic Examiners Disagree: Bias, or Just Inaccuracy?

AU Mossman, D
AF Mossman, Douglas
TI When Forensic Examiners Disagree: Bias, or Just Inaccuracy?
AB Previous investigators have suggested that bias might account for the
disparate rates at which examiners conclude that defendants are
competent to stand trial (CST). This article describes three computer
studies of how biases and imperfect accuracy might affect rates of
disagreement. Study 1 assumed that examiners could discriminate between
competent and incompetent accurately (effect size = 1.81, receiver
operating characteristic area = 0.90) and used computer simulation of
20,000 pairs of CST evaluations to determine how different judgment
thresholds (e. g., thresholds exemplifying biases toward opinions that
defendants were competent or incompetent) would elevate disagreement
rates above those expected through chance error alone. Studies 2 and 3
evaluated the assumptions of Study 1 using previously published data to
make inferences about examiner accuracy and threshold locations.
Imperfect accuracy alone would often explain much between-examiner
disagreement, even if examiners approached evaluations with distinct
biases. Results from Studies 2 and 3 suggested that assumptions used in
Study 1 were reasonable. Many instances of between-examiner disagreement
might be attributable to imperfect accuracy that expresses itself in
random errors, rather than to examiner biases that imply different
thresholds for judging defendants' competence.
PY 2013
VL 19
IS 1
BP 40
EP 55