Nature of Case: In 1994, Kansas established legal procedures providing for the indefinite detention of persons who, due to a “mental abnormality” or “personality disorder” are likely to engage in “predatory acts of sexual violence.” Hendricks was the first person to become subject to the law, who challenged it on grounds of Substantive Due Process, Double Jeopardy, and Ex Post Facto. The Kansas Supreme Court invalidated the law on due process grounds, finding that the “mental abnormality” requirement was not sufficiently determinative, and the state sought review from the United States Supreme Court, which was grated.
Holding: Supreme Court reversed. The requirement of mental abnormality was not sufficiently vague so as to violate due process requirements, which the Court noted were not absolute in this context. Furthermore, the Court concluded that — the question of treatment notwithstanding — the Act was non-punitive and therefore did not offend constitutional provisions relating to Double Jeopardy or Ex Post Facto punishments.