Neuropsychological Assessment Evidence in Court: Quality and Challenges to Admissibility

When questions about a person’s mental state arise in court, psychologists are often called in to help. Psychological assessment tools are routinely included in these evaluations to inform legal decision making. In accordance with the Daubert standard, which governs the admissibility of expert testimony, courts are obligated to exclude evidence that relies on poor scientific practice, including assessment tools. However, prior research demonstrates that psychological assessment tools with weak psychometric properties are routinely admitted in court, rarely challenged on the basis of their reliability, and if a challenge is indeed raised, often still admitted (Neal et al., 2019). Is neuropsychological assessment evidence in particular vulnerable to the same pitfalls? The present research aimed to 1) quantify the quality of neuropsychological assessment evidence used in court, 2) evaluate whether courts are calibrated to the quality of these tools through the rate and success of legal admissibility challenges raised, and 3) compare forensic mental health evaluators’ experiences and practices with regard to the quality of neuropsychological versus non-neuropsychological assessment tools. Neuropsychological tools appeared to perform worse than non-neuropsychological tools in terms of psychometric quality. However, in a case law analysis, significantly fewer challenges were observed to the legal admissibility of neuropsychological tools than to non-neuropsychological tools. To protect the legitimacy of the legal system and prevent wrongful decisions, it is critical that the evidence on which psychologists’ expert opinions are formed is scientifically valid, and that judges and attorneys adequately scrutinize the quality of evidence introduced in court.