O'Connor v. Donaldson, 422 U.S. 563 (1975), was a landmark decision of the US Supreme Court in mental health law ruling that a state cannot constitutionally confine a non-dangerous individual who is capable of surviving safely in freedom by themselves or with the help of willing and responsible family members or friends.

[4] Kenneth Donaldson (confined patient) had been held for 15 years in Florida State Hospital at Chattahoochee, due to needs of "care, maintenance, and treatment."

[6] A finding of "mental illness" alone cannot justify a State's locking a person up against his will and keeping him indefinitely in simple custodial confinement.

May the State confine the mentally ill merely to ensure them a living standard superior to that they enjoy in the private community?

Moreover, while the State may arguably confine a person to save him from harm, incarceration is rarely if ever a necessary condition for raising the living standards of those capable of surviving safely in freedom, on their own or with the help of family or friends.

In short, a State cannot constitutionally confine without more a non-dangerous individual who is capable of surviving safely in freedom by himself or with the help of willing and responsible family members or friends.