Abstract:
Mental health experts are increasingly being utilised by the criminal justice system to provide assistance to courts
during the assessment of issues falling beyond the knowledge and/or experience of the courts. A particular domain
where the assistance of qualified psychiatrists and psychologists is becoming essential is where the defence of
pathological criminal incapacity falls to be assessed. Mental health professionals testifying during trials where the
defence of pathological criminal incapacity is raised will present opinion evidence which is one of the exceptions
to the rule of inadmissibility of opinion evidence. Mental health professionals providing their opinion evidence
are, however, prohibited from expressing opinions on so-called “ultimate issues” upon which only the court may
ultimately rule upon. The latter rule is also commonly known in practice as the “ultimate issue” rulewhich presents
multifaceted challenges in respect of the application of the defence of pathological criminal incapacity. In this article,
the author assesses the application of the ultimate issue rule with reference to the defence of pathological criminal
incapacity as it operates within the South African criminal law context. A comparative analysis is also provided with
reference to the rule as it operates in the United States of America and more specifically Federal Rule 704. It is
concluded that the ultimate issue rule unnecessarily restricts testimony provided by mental health professionals
as such placing a barrier on such evidence. As such, it is argued that the rule is superfluous as it remains within
the discretion of the trier of fact to decide as to what weight to attach to such evidence.
