Cal. Civ. Proc. Code § 1985.8

(a)
1. (1) A subpoena in a civil proceeding may require that electronically stored information, as defined in Section 2016.020, be produced and that the party serving the subpoena, or someone acting on the party’s request, be permitted to inspect, copy, test, or sample the information.
2. (2) Any subpoena seeking electronically stored information shall comply with the requirements of this chapter.
(b) A party serving a subpoena requiring production of electronically stored information may specify the form or forms in which each type of information is to be produced.
(c) If a person responding to a subpoena for production of electronically stored information objects to the specified form or forms for producing the information, the subpoenaed person may provide an objection stating the form or forms in which it intends to produce each type of information.
(d) Unless the subpoenaing party and the subpoenaed person otherwise agree or the court otherwise orders, the following shall apply:
1. (1) If a subpoena requiring production of electronically stored information does not specify a form or forms for producing a type of electronically stored information, the person subpoenaed shall produce the information in the form or forms in which it is ordinarily maintained or in a form that is reasonably usable.
2. (2) A subpoenaed person need not produce the same electronically stored information in more than one form.
(e) The subpoenaed person opposing the production, inspection, copying, testing, or sampling of electronically stored information on the basis that information is from a source that is not reasonably accessible because of undue burden or expense shall bear the burden of demonstrating that the information is from a source that is not reasonably accessible because of undue burden or expense.
(f) If the person from whom discovery of electronically stored information is subpoenaed establishes that the information is from a source that is not reasonably accessible because of undue burden or expense, the court may nonetheless order discovery if the subpoenaing party shows good cause, subject to any limitations imposed under subdivision (i).
(g) If the court finds good cause for the production of electronically stored information from a source that is not reasonably accessible, the court may set conditions for the discovery of the electronically stored information, including allocation of the expense of discovery.
(h) If necessary, the subpoenaed person, at the reasonable expense of the subpoenaing party, shall, through detection devices, translate any data compilations included in the subpoena into a reasonably usable form.
(i) The court shall limit the frequency or extent of discovery of electronically stored information, even from a source that is reasonably accessible, if the court determines that any of the following conditions exists:
1. (1) It is possible to obtain the information from some other source that is more convenient, less burdensome, or less expensive.
2. (2) The discovery sought is unreasonably cumulative or duplicative.
3. (3) The party seeking discovery has had ample opportunity by discovery in the action to obtain the information sought.
4. (4) The likely burden or expense of the proposed discovery outweighs the likely benefit, taking into account the amount in controversy, the resources of the parties, the importance of the issues in the litigation, and the importance of the requested discovery in resolving the issues.
(j) If a subpoenaed person notifies the subpoenaing party that electronically stored information produced pursuant to a subpoena is subject to a claim of privilege or of protection as attorney work product, as described in Section 2031.285, the provisions of Section 2031.285 shall apply.
(k) A party serving a subpoena requiring the production of electronically stored information shall take reasonable steps to avoid imposing undue burden or expense on a person subject to the subpoena.
(l) An order of the court requiring compliance with a subpoena issued under this section shall protect a person who is neither a party nor a party’s officer from undue burden or expense resulting from compliance.
(m)
1. (1) Absent exceptional circumstances, the court shall not impose sanctions on a subpoenaed person or any attorney of a subpoenaed person for failure to provide electronically stored information that has been lost, damaged, altered, or overwritten as the result of the routine, good faith operation of an electronic information system.
2. (2) This subdivision shall not be construed to alter any obligation to preserve discoverable information.