In Allen v. Illinois, the U.S. Supreme Court ruled that a state's civil commitment proceedings for sexually dangerous persons did not qualify as criminal prosecution, thus individuals subjected to such proceedings were not entitled to the same constitutional protections afforded in criminal trials under the Fifth and Fourteenth Amendments. The case involved Terry Allen who was committed by an Illinois court as a sexually dangerous person after being convicted of multiple sex offenses against minors. He argued that he should have been given certain rights typically granted in criminal cases including protection from self-incrimination and proof beyond reasonable doubt before his commitment could be extended indefinitely. However, the Supreme Court held that since these commitments are intended more for treatment rather than punishment, they do not constitute "criminal" procedures per se and therefore don't warrant all safeguards provided in such cases.

In the dissenting opinion for Allen v. Illinois, Justice Thurgood Marshall argued that civil commitment proceedings should be treated as criminal and thus subject to constitutional protections of the Fifth Amendment. He disagreed with the majority's view that such proceedings are not punitive but rather preventative or remedial in nature. Marshall contended that a person subjected to involuntary confinement suffers a significant deprivation of liberty, which is essentially punishment regardless of its label or purpose. Therefore, he believed individuals facing civil commitment should have rights against self-incrimination under the Fifth Amendment just like defendants in criminal cases do.