Welf. & Inst. Code, § 5171

(a) If the facility for 72-hour treatment and evaluation of individuals under the influence of alcohol admits the person, it may detain the individual for evaluation and detoxification treatment, and such other treatment as may be indicated, for a period not to exceed 72 hours. Saturdays, Sundays, and holidays shall be included for the purpose of calculating the 72-hour period. However, an individual may voluntarily remain in the facility for more than 72 hours if the professional person in charge of the facility determines the individual is in need of and may benefit from further treatment and care, provided any individual who is taken or caused to be taken to the facility shall have priority for available treatment and care over an individual who has voluntarily remained in a facility for more than 72 hours.

(b) If in the judgment of the professional person in charge of the facility providing evaluation and treatment, the person can be properly served without being detained, the individual shall be provided evaluation, detoxification treatment or other treatment, crisis intervention, or other inpatient or outpatient services on a voluntary basis.