A5150is aninvoluntary72-hour hold in a psychiatric facility, for evaluation. Apeace officer,registered nurse, medical doctor, or certain other categories of people may place the hold. Three criteria apply to this section: a danger to themselves, a danger to others, or gravely disabled. A qualified officer, which includes any Californiapeace officer, as well as any specifically-designated county clinician, can request the confinement after signing a written declaration stating the psychiatric diagnosis that the diagnosing medical professional believes to be the cause or reason why they believe the patient to be "a danger to themselves or others" or the psychiatric disorder that has rendered the patient incapable of making their own medical treatment decisions.
In informal usage,5150(pronounced "fifty-one-fifty") can refer to the person being confined (e.g., "I have a possible 5150 here"), the declaration, or the act of committing someone (as in "(Someone) was 5150ed").