California Code, Evidence Code - EVID § 1228.1

(a) Except as provided in subdivision (b), neither the signature of any parent or legal guardian on a child welfare services case plan nor the acceptance of any services prescribed in the child welfare services case plan by any parent or legal guardian shall constitute an admission of guilt or be used as evidence against the parent or legal guardian in a court of law.

(b) A parent's or guardian's failure to cooperate, except for good cause, in the provision of services specified in the child welfare services case plan may be used as evidence, if relevant, in any hearing held pursuant to Section 366.21, 366.22, or 388 of the Welfare and Institutions Codeand at any jurisdictional or dispositional hearing held on a petition filed pursuant to Section 300, 342, or 387 of the Welfare and Institutions Code.