Poster A132, Saturday, March 25, 5:00 – 7:00 pm, Pacific Concourse
Group-to-individual (G2i) inferences in neuropsychological expert testimony: How the legal system understands averaged brain data
Valerie Hardcastle1, MK Kitzmiller1, Shelby Lahey1; 1University of Cincinnati
While the behavioral tests used by neuropsychologists have a long history of detailed studies validating their use as diagnostics on individuals, the same cannot be said for brain imaging protocols. Several legal scholars have raised concerns regarding the use of neuropsychological data in criminal trials. In particular, their concern is that clinicians diagnose brain deficits by comparing their patient’s brain scan with averaged scans of normal individuals to pinpoint any differences that might be relevant to behavior. However individual differences can and often do swamp group effects. Consequently, data from these types of studies can make it difficult to diagnose any particular behavioral or cognitive deficiency in a single individual based on comparison with a group. However, it is only now that these data have been proffered often enough in court cases that we are able to analyze their actual use. This study analyzes 3,000+ published appellate decisions from Oct 2014-Oct 2016 in which brain data are cited in the decision. Of those, 326 relied on G2i inferences. Using mixed-method quantitative and qualitative analyses of the written decisions, we demonstrate the following: (1) G2i inferences support three broad diagnostic categories: Mental Disorders, Effects of Substance Use, and Minors/Developmental Disorders; (2) G2i inferences in legal cases appropriately rely on data triangulation from a variety of sources; and (3) Faigman et al.’s (2014) recommendations regarding admissibility standards and best practices for G2i inferences do not reflect actual use. We conclude that concerns regarding G2i inferences in a legal context are not warranted.
Topic Area: OTHER