In Re Lois M.

J.—Petitioner, Lois M., challenges her confinement in the locked mental health ward of Marin General Hospital. The decision to place her in the facility was made by her temporary conservator, the Public Guardian of the County of Marin, appointed pursuant to the provisions of the Lanterman-Petris-Short Act (LPS). (See Welfare and Institutions Code sections 5352.1, 5353, 5358.) Protesting both her confinement and the fact of the appointment of the temporary conservator (Conservatorship of Early (1983) 35 Cal.3d 244, 255 [ 197 Cal.Rptr. 539 , 673 P.2d 209 ]), appellant contends that the burden of proof must be placed on the county to justify her detention beyond a reasonable doubt or, at a minimum, by clear and convincing evidence. Respondent, County of Marin, urges that it was required only to demonstrate by a preponderance of the evidence that proper procedures had been followed in the making of the placement choice and that there was probable cause for the temporary conservator’s decision; that upon such showing, the burden of proof shifted to petitioner to prove that there was no probable cause for her detention.

We hold that the county must justify petitioner’s…