CA Civ Proc Code Section 2034.450

(a)

The party taking the deposition of an expert witness shall either accompany the service of the deposition notice with a tender of the expert’s fee based on the anticipated length of the deposition, or tender that fee at the commencement of the deposition.

(b)

The expert’s fee shall be delivered to the attorney for the party designating the expert.

(c)

If the deposition of the expert takes longer than anticipated, the party giving notice of the deposition shall pay the balance of the expert’s fee within five days of receipt of an itemized statement from the expert.