CAL. FAM. CODE § 7551 : California Code - Section 7551

In a civil action or proceeding in which paternity is a relevant fact, the court may upon its own initiative or upon suggestion made by or on behalf of any person who is involved, and shall upon motion of any party to the action or proceeding made at a time so as not to delay the proceedings unduly, order the mother, child, and alleged father to submit to genetic tests. If a party refuses to submit to the tests, the court may resolve the question of paternity against that party or enforce its order if the rights of others and the interests of justice so require. A party's refusal to submit to the tests is admissible in evidence in any proceeding to determine paternity. For the purposes of this chapter, "genetic tests" means any genetic test that is generally acknowledged as reliable by accreditation bodies designated by the United States Secretary of Health and Human Services.