CCP §2033.300: (a) A party may withdraw or amend an admission made in response to a request for admission only on leave of court granted after notice to all parties.

(a) A party may withdraw or amend an admission made in response to a request for admission only on leave of court granted after notice to all parties. (b) The court may permit withdrawal or amendment of an admission only if it determines that the admission was the result of mistake, inadvertence, or excusable neglect, and that the party who obtained the admission will not be substantially prejudiced in maintaining that party’s action or defense on the merits. (c) The court may impose conditions on the granting of the motion that are just, including, but not limited to, the following: (1) An order that the party who obtained the admission be permitted to pursue additional discovery related to the matter involved in the withdrawn or amended admission. (2) An order that the costs of any additional discovery be borne in whole or in part by the party withdrawing or amending the admission.