In Ake v. Oklahoma, the U.S Supreme Court ruled in 1984 that when a defendant's mental health is a significant factor at trial, the state must provide an indigent defendant with access to a psychiatric examination and assistance if the defendant cannot afford these services. The case involved Glen Burton Ake who was charged with murder but claimed insanity as his defense. He requested for state-provided psychiatric assistance which was denied by Oklahoma courts leading to his conviction. Upon appeal, the Supreme Court held that due process requires states to provide such resources for indigent defendants because of their fundamental fairness in ensuring an accurate resolution of sanity issues at stake during trials.

In the dissenting opinion for Ake v. Oklahoma, Justice Rehnquist argued that the majority had overstepped its bounds by creating a new constitutional right to psychiatric assistance for indigent defendants in capital cases. He contended that this decision was not supported by precedent or historical practice and could lead to an unmanageable expansion of rights for criminal defendants at public expense. Furthermore, he questioned whether such expert assistance would actually contribute significantly to the fairness of trials or just add unnecessary complexity and cost. He also expressed concern about potential abuses of this right, including frivolous requests for experts and manipulation of diagnoses. Ultimately, he believed it should be left up to states or legislatures rather than courts to decide on providing such resources.