Integrated expertise in legal psychology with the use of handwritten document analysis

Psychological expertise in the legal context is complex because traditionally used instruments may be less reliable. Therefore, experts must be cautious when evaluating typical questionnaire-based self-assessment tests. This is because of known issues such as systematic biases, natural subjectivity, context-dependency, social desirability, and ambiguity of questionnaire items. It is important to use clear and concise language, avoid biased or emotional language, and maintain a formal register. Tests should be combined with other methods in the legal context due to the potential untrustworthiness of respondents. Handwriting analysis is a nonverbal and external assessment that can add objectivity and reliability when applied in a formalized and validated manner. Furthermore, analysing handwritten documents can help evaluate a person’s cognitive condition, especially in their absence, which is often crucial in legal cases. The article demonstrates the integration of the computer-aided HSDetect system, which uses handwriting-based methods, with psychometric instruments such as the Eysenck Personality Inventory (EPI), Buss-Perry Aggression Questionnaire (BPAQ), and Leonhard–Shmishek Test (LST) on real cases. It discusses the methodological aspects and problems of integrating these methods.