Cal. Welf. and Inst. Code § 625.1
Any minor who is taken into temporary custody pursuant to subdivision (a) of Section 625, when the peace officer has reasonable cause for believing the minor is a person described in Section 602, or pursuant to subdivision (b) or (c) of Section 625, may be requested to submit to voluntary chemical testing of his or her urine for the purpose of determining the presence of alcohol or illegal drugs. The peace officer shall inform the minor that the chemical test is voluntary. The results of this test may be considered by the court in determining the disposition of the minor pursuant to Section 706 or 777. Unless otherwise provided by law, the results of such a test shall not be the basis of a petition filed by the prosecuting attorney to declare the minor a person described in Section 602, nor shall it be the basis for such a finding by a court pursuant to Section 702.
Ca. Welf. and Inst. Code § 625.1