Abstract
Testimony about the future dangerousness of a person has become a central staple
of many judicial processes. In settings such as bail, sentencing, and parole decisions,
in rulings about the civil confinement of the mentally ill, and in custody decisions
in a context of domestic violence, the assessment of a person’s propensity
towards physical or sexual violence is regarded as a deciding factor. These assessments
can be based on two forms of expert testimony: actuarial or clinical. The
purpose of this paper is to examine the scientific and epistemological basis of both
methods of prediction or risk assessment. My analysis will reveal that this kind of
expert testimony is scientifically baseless. The problems I will discuss will generate
a dilemma for factfinders: on the one hand, given the weak predictive abilities of
the branches of science involved, they should not admit expert clinical or actuarial
testimony as evidence; on the other hand, there is a very strong tradition and a vast
jurisprudence that supports the continued use of this kind of expert testimony. It is
a clear case of the not so uncommon conflict between science and legal tradition.