By the time a forensic psychologist takes the stand as an expert witness, the meaningful work of defending a criminal forensic assessment has already happened. Cross-examination only surfaces what the assessment file contains (or doesn’t). Motions in limine, pre-trial requests to exclude certain arguments or pieces of evidence, challenge the report's assertions. The Rule 702 standard, which governs the admissibility of expert testimony in federal court and most state systems modeled on it, is best understood as a quality-control framework that should shape decisions made weeks or months before any testimony is given. This quality-control function is especially true after the December 2023 amendments to Rule 702, which clarified that the proponent of expert testimony must demonstrate admissibility by a preponderance of the evidence and that an expert's opinion must stay within the bounds of what the underlying methodology actually supports.
Anticipating a Rule 702 challenge means treating each phase of the assessment as a future evidentiary record. The data collected, the methods selected, the inferences drawn, and the language used in the report will all be evaluated against the four prongs of the rule: that the testimony will help the trier of fact (the person or group evaluating evidence), that it is based on sufficient facts or data, that it is the product of reliable principles and methods, and that those principles and methods have been reliably applied to the facts of the case.