Code Civ. Proc., § 1141.21

(a) (1) If the judgment upon the trial de novo is not more favorable in either the amount of damages awarded or the type of relief granted for the party electing the trial de novo than the arbitration award, the court shall order that party to pay the following nonrefundable costs and fees, unless the court finds in writing and upon motion that the imposition of these costs and fees would create such a substantial economic hardship as not to be in the interest of justice:

(A) To the court, the compensation actually paid to the arbitrator, less any amount paid pursuant to subparagraph (D).

(B) To the other party or parties, all costs specified in Section 1033.5, and the party electing the trial de novo shall not recover his or her costs.

(C) To the other party or parties, the reasonable costs of the services of expert witnesses, who are not regular employees of any party, actually incurred or reasonably necessary in the preparation or trial of the case.

(D) To the other party or parties, the compensation paid by the other party or parties to the arbitrator, pursuant to subdivision (b) of Section 1141.28.

(2) Those costs and fees, other than the compensation of the arbitrator, shall include only those incurred from the time of election of the trial de novo.

(b) If the party electing the trial de novo has proceeded in the action in forma pauperis and has failed to obtain a more favorable judgment, the costs and fees under subparagraphs (B) and (C) of paragraph (1) of subdivision (a) shall be imposed only as an offset against any damages awarded in favor of that party.

(c) If the party electing the trial de novo has proceeded in the action in forma pauperis and has failed to obtain a more favorable judgment, the costs under subparagraph (A) of paragraph (1) of subdivision (a) shall be imposed only to the extent that there remains a sufficient amount in the judgment after the amount offset under subdivision (b) has been deducted from the judgment.