(D) Expert Employed Only for Trial Preparation. Ordinarily, a party may not, by interrogatories or deposition, discover facts known or opinions held by an expert who has been retained or specially employed by another party in anticipation of litigation or to prepare for trial and who is not expected to be called as a witness at trial. But a party may do so only:
(i) as provided in Rule 35(b); or
(ii) on showing exceptional circumstances under which it is impracticable for the party to obtain facts or opinions on the same subject by other means.
(E) Payment. Unless manifest injustice would result, the court must require that the party seeking discovery:
(i) pay the expert a reasonable fee for time spent in responding to discovery under Rule 26(b)(4)(A) or (D); and
(ii) for discovery under (D), also pay the other party a fair portion of the fees and expenses it reasonably incurred in obtaining the expert's facts and opinions.

(5) Claiming Privilege or Protecting Trial-Preparation Materials.
(A) Information Withheld. When a party withholds information otherwise discoverable by claiming that the information is privileged or subject to protection as trial-preparation material, the party must:
(i) expressly make the claim; and
(ii) describe the nature of the documents, communications, or tangible things not produced or dis-closed一and do so in a manner that, without revealing information itself privileged or protected, will enable other parties to assess the claim.
(B) Information Produced. If information produced in discovery is subject to a claim of privilege or of protection as trial-preparation material, the party making the claim may notify any party that received the information of the claim and the basis for it. After being notified, a party must promptly return, sequester, or destroy the specified information and any copies it has; must not use or disclose the information until the claim is resolved; must take reasonable steps to retrieve the information if the party disclosed it before being notified; and may promptly present the information to the court under seal for a determination of the claim. The producing party must preserve the information until the claim is resolved.

(c) Protective Orders.
(1) In General. A party or any person from whom discovery is sought may move for a protective order in the court where the action is pending一or as an alternative on matters relating to a deposition, in the court for the district where the deposition will be taken. The motion must include a certification that the movant has in good faith conferred or attempted to confer with other affected parties in an effort to resolve the dispute without court action. The court may, for good cause, issue an order to protect a party or person from annoyance, embarrassment, oppression, or undue burden or expense, including one or more of the following:
(A) forbidding the disclosure or discovery;
(B) specifying terms, including time and place or the allocation of expenses, for the disclosure or discovery;
(C) prescribing a discovery method other than the one selected by the party seeking discovery;
(D) forbidding inquiry into certain matters, or limiting the scope of disclosure or discovery to certain matters;
(E) designating the persons who may be present while the discovery is conducted;
(F) requiring that a deposition be sealed and opened only on court order;
(G) requiring that a trade secret or other confidential research, development, or commercial information not be revealed or be revealed only in a specified way; and
(H) requiring that the parties simultaneously file specified documents or information in sealed envelopes, to be opened as the court directs.
(2) Ordering Discovery. If a motion for a protective order is wholly or partly denied, the court may, on just terms, order that any party or person provide or permit discovery.
(3) Awarding Expenses. Rule 37(a)(5) applies to the award of expenses.

(d) Timing and Sequence of Discovery.
(1) Timing. A party may not seek discovery from any source before the parties have conferred as required by Rule 26(f), except in a proceeding exempted from initial disclosure under Rule 26(a)(1)(B), or when authorized by these rules, by stipulation, or by court order.
(2) Early Rule 34 Requests.
(A) Time to Deliver. More than 21 days after the summons and complaint are served on a party, a request under Rule 34 may be delivered:
(i) to that party by any other party, and
(ii) by that party to any plaintiff or to any other party that has been served.
(B) When Considered Served. The request is considered to have been served at the first Rule 26(f) conference.
(3) Sequence. Unless the parties stipulate or the court orders otherwise for the parties' and witnesses' convenience and in the interests of justice:
(A) methods of discovery may be used in any sequence; and
(B) discovery by one party does not require any other party to delay its discovery.

(e) Supplementing Disclosures and Responses.
(1) In General. A party who has made a disclosure under Rule 26(a)一or who has responded to an interrogatory, request for production, or request for admission一must supplement or correct its disclosure or response:
(A) in a timely manner if the party learns that in some material respect the disclosure or response is incomplete or incorrect, and if the additional or corrective information has not otherwise been made known to the other parties during the discovery process or in writing; or
(B) as ordered by the court.
(2) Expert Witness. For an expert whose report must be disclosed under Rule 26(a)(2)(B), the party's duty to supplement extends both to information included in the report and to information given during the expert's deposition. Any additions or changes to this information must be disclosed by the time the party's pretrial disclosures under Rule 26(a)(3) are due.

(f) CONFERENCE OF THE PARTIES； PLANNING FOR DISCOVERY.
(1) Conference Timing. Except in a proceeding exempted from initial disclosure under Rule 26(a)(1)(B) or when the court orders otherwise, the parties must confer as soon as prac-ticable一and in any event at least 21 days before a scheduling conference is to be held or a scheduling order is due under Rule 16(b).
(2) Conference Content; Parties' Responsibilities. In conferring, the parties must consider the nature and basis of their claims and defenses and the possibilities for promptly settling or resolving the case; make or arrange for the disclosures required by Rule 26(a)(1); discuss any issues about preserving discoverable information; and develop a proposed discovery plan. The attorneys of record and all unrepresented parties that have appeared in the case are jointly responsible for arranging the conference, for attempting in good faith to agree on the proposed discovery plan, and for submitting to the court within 14 days after the conference a written report outlining the plan. The court may order the parties or attorneys to attend the conference in person.

(3) Discovery Plan. A discovery plan must state the parties' views and proposals on:
(A) what changes should be made in the timing, form, or requirement for disclosures under Rule 26(a), including a statement of when initial disclosures were made or will be made;
(B) the subjects on which discovery may be needed, when discovery should be completed, and whether discovery should be conducted in phases or be limited to or focused on particular issues;
(C) any issues about disclosure, discovery, or preservation of electronically stored information, including the form or forms in which it should be produced;
(D) any issues about claims of privilege or of protection as trial-preparation materials, including一if the parties agree on a procedure to assert these claims after produc-tion一whether to ask the court to include their agreement in an order under Federal Rule of Evidence 502;
(E) what changes should be made in the limitations on discovery imposed under these rules or by local rule, and what other limitations should be imposed; and
(F) any other orders that the court should issue under Rule 26(c) or under Rule 16(b) and (c).

(4) Expedited Schedule. If necessary to comply with its expedited schedule for Rule 16(b) conferences, a court may by local rule:
(A) require the parties' conference to occur less than 21 days before the scheduling conference is held or a scheduling order is due under Rule 16(b); and
(B) require the written report outlining the discovery plan to be filed less than 14 days after the parties' conference, or excuse the parties from submitting a written report and permit them to report orally on their discovery plan at the Rule 16(b) conference.

(g) Signing Disclosures and Discovery Requests, Responses, and Objections.
(1) Signature Required; Effect of Signature. Every disclosure under Rule 26(a)(1) or (a)(3) and every discovery request, response, or objection must be signed by at least one attorney of record in the attorney's own name一or by the party personally, if unrepresented一and must state the signer's address, email address, and telephone number. By signing, an attorney or party certifies that to the best of the person's knowledge, information, and belief formed after a reasonable inquiry:
(A) with respect to a disclosure, it is complete and correct as of the time it is made; and
(B) with respect to a discovery request, response, or objection, it is:
(i) consistent with these rules and warranted by existing law or by a nonfrivolous argument for extending, modifying, or reversing existing law, or for establishing new law;
(ii) not interposed for any improper purpose, such as to harass, cause unnecessary delay, or needlessly increase the cost of litigation; and
(iii) neither unreasonable nor unduly burdensome or expensive, considering the needs of the case, prior discovery in the case, the amount in controversy, and the importance of the issues at stake in the action.

(2) Failure to Sign. Other parties have no duty to act on an unsigned disclosure, request, response, or objection until it is signed, and the court must strike it unless a signature is promptly supplied after the omission is called to the attorney's or party's attention.
(3) Sanction for Improper Certification. If a certification violates this rule without substantial justification, the court, on motion or on its own, must impose an appropriate sanction on the signer, the party on whose behalf the signer was acting, or both. The sanction may include an order to pay the reasonable expenses, including attorney's fees, caused by the violation.
(As amended Dec. 27, 1946, eff. Mar. 19, 1948; Jan. 21, 1963, eff. July 1, 1963; Feb. 28, 1966, eff. July 1, 1966; Mar. 30, 1970, eff. July 1, 1970; Apr. 29, 1980, eff. Aug. 1, 1980; Apr. 28, 1983, eff. Aug. 1, 1983; Mar. 2, 1987, eff. Aug. 1, 1987; Apr. 22, 1993, eff. Dec. 1, 1993; Apr. 17, 2000, eff. Dec. 1, 2000; Apr. 12, 2006, eff. Dec. 1, 2006; Apr. 30, 2007, eff. Dec. 1, 2007; Apr. 28, 2010, eff. Dec. 1, 2010; Apr. 29, 2015, eff. Dec. 1, 2015.)