Abstract
The structure of the legal concept of unfitness to stand trial and how it corresponds to psychometric concepts is examined. We conclude that psychometric attempts at quantification and measurement are logically flawed, because they inappropriately treat fitness/unfitness as an individual trait rather than as situation-specific conjunctive/disjunctive concepts. It is argued that, whereas psychometric approaches may be suitable for measuring single components of unfitness, an overall “fitness” score is meaningless and that the assessment should focus on elements of unfitness. The determination of unfitness requires the simultaneous consideration of several different individual capabilities in reference to the demands of a specific trial. The quantification of these specific capabilities by psychologists can assist psychiatrists and the court, but the evaluation of their influence on unfitness in the instant case must be left to the court.