California Code, Code of Civil Procedure - CCP § 2034.430

(a) Except as provided in subdivision (f), this section applies to an expert witness, other than a party or an employee of a party, who is any of the following:

(b) A party desiring to depose an expert witness described in subdivision (a) shall pay the expert's reasonable and customary hourly or daily fee for any time spent at the deposition from the time noticed in the deposition subpoena, or from the time of the arrival of the expert witness should that time be later than the time noticed in the deposition subpoena, until the time the expert witness is dismissed from the deposition, regardless of whether the expert is actually deposed by any party attending the deposition.

(c) If any counsel representing the expert or a nonnoticing party is late to the deposition, the expert's reasonable and customary hourly or daily fee for the time period determined from the time noticed in the deposition subpoena until the counsel's late arrival, shall be paid by that tardy counsel.

(d) Notwithstanding subdivision (c), the hourly or daily fee charged to the tardy counsel shall not exceed the fee charged to the party who retained the expert, except where the expert donated services to a charitable or other nonprofit organization.

(e) A daily fee shall only be charged for a full day of attendance at a deposition or where the expert was required by the deposing party to be available for a full day and the expert necessarily had to forgo all business that the expert would otherwise have conducted that day but for the request that the expert be available all day for the scheduled deposition.

(f) In a worker's compensation case arising under Division 4 (commencing with Section 3201) or Division 4.5 (commencing with Section 6100) of the Labor Code, a party desiring to depose any expert on another party's expert witness list shall pay the fee under this section.