Assessment of testamentary capacity: a systematic review of legal, neuropsychological, and bioethical perspectives across jurisdictions

Background. Testamentary capacity (TC) refers to an individual’s legal and cognitive ability to create or modify a valid will. The assessment of TC becomes particularly challenging in individuals with neurodegenerative and psychiatric disorders. While many jurisdictions have established legal criteria for evaluating TC, diagnostic and evaluative processes vary significantly across countries. This review synthesizes existing research on TC assessments, focusing on the methodologies, bioethical considerations, and legal frameworks utilized in different countries. Special emphasis is placed on the importance of evaluating cognitive abilities, including memory, comprehension, and decision-making, which are crucial for determining TC. Methods. A systematic review was conducted in accordance with the PRISMA guidelines. Articles were identified through searches in the PubMed, Scopus, and Web of Science databases, supplemented by grey literature from Google Scholar. The search strategy employed Boolean keyword combinations related to testamentary capacity (TC), dementia, cognitive assessment, and bioethics. Studies that addressed bioethical considerations and provided specific measures for TC evaluation were included. Results. The analysis revealed significant variability in both legal and medical approaches to testamentary capacity (TC) assessments across different countries. Some studies emphasize the importance of the “lucid interval” in dementia patients, suggesting that fluctuating cognitive abilities can influence will-making decisions (Shulman et al., 2015). Other research focuses on the legal implications of deathbed wills, where diminished cognitive functioning near the end of life complicates TC evaluations (Purser & Rosenfeld, 2016). Neurolaw has provided a framework for understanding the impact of historical cases, such as Banks v Goodfellow (1870), which continues to serve as a reference point for modern assessments (Bennett, 2016). The role of neuropsychological tools in evaluating undue influence and cognitive abilities also emerged as a critical factor (Kaufmann, 2016). Recent advances in artificial intelligence (AI) present both opportunities and challenges for TC evaluations, particularly in the context of dementia (Economou & Kontos, 2023). Conclusion.The review highlights significant variability in testamentary capacity (TC) assessment methodologies across different countries. While legal precedents such as Banks v Goodfellow (Bennett, 2016) continue to influence current practice, the introduction of AI and other modern tools presents both opportunities and ethical challenges for future assessments (Economou & Kontos, 2023). Incorporating consistent bioethical frameworks and standardized neuropsychological assessments could help ensure more reliable and equitable TC evaluations across various jurisdictions.