Causal attribution in forensic psychological injury: legal causation, validity assessment, and expert reasoning

Forensic psychological injury evaluations often require an opinion on whether post-event symptoms are attributable to a specific accident, assault, workplace exposure, institutional event, or alleged abuse. Such opinions cannot rest on temporal sequence, clinical plausibility, or the presence of a trauma-related diagnosis alone. This conceptual analysis argues that defensible causal attribution requires coordination of three elements that are often handled separately: legal causation concepts, psychological causal reasoning, and validity assessment. The article distinguishes event occurrence, psychological injury, functional impairment, and imputability of injury to the event. It then discusses but-for causation, material contribution, proximate or legal causation in common-law settings, and the broader problem of imputability in civil-law contexts. The article further argues that performance validity tests, symptom validity tests, and broader response-validity analysis are not ancillary psychometric issues but conditions that shape the permissible strength of causal conclusions. A revised framework is proposed that distinguishes direct causation, material contributory causation, indirect causal pathways, and insufficient basis for attribution, while treating precipitating, exacerbating, accelerating, cumulative, and perpetuating effects as modifiers. The framework is positioned relative to prior work on psychological injury, malingering, and forensic evaluation, and is translated into a practical reporting sequence, a short vignette, and calibrated wording for expert reports.