Part I. General Rules
Rule 1. 
A party's duty to amend and supplement written discovery regarding a testifying expert is governed by Rule 193.5. If an expert witness is retained by, employed by, or otherwise under the control of a party, that party must also amend or supplement any deposition testimony or written report by the expert, but only with regard to the expert's mental impressions or opinions and the basis for them.
When a party takes the oral deposition of an expert witness retained by the opposing party, all reasonable fees charged by the expert for time spent in preparing for, giving, reviewing, and correcting the deposition must be paid by the party that retained the expert.
This rule does not limit the permissible methods of discovery concerning consulting experts whose mental impressions or opinions have been reviewed by a testifying expert. See Rule 192.3(e). Information concerning purely consulting experts, of course, is not discoverable.
This rule and Rule 194 do not address depositions of testifying experts who are not retained by, employed by, or otherwise subject to the control of the responding party, nor the production of the materials identified in Rule 192.3(e)(5) and (6) relating to such experts. Parties may obtain this discovery, however, through Rules 176 and 205.
In scheduling the designations and depositions of expert witnesses, the rule attempts to minimize unfair surprise and undue expense. A party seeking affirmative relief must either produce an experts report or tender the expert for deposition before an opposing party is required to designate experts. A party who does not wish to incur the expense of a report may simply tender the expert for deposition, but a party who wishes an expert to have the benefit of an opposing partys experts opinions before being deposed may trigger designation by providing a report. Rule 191.1 permits a trial court, for good cause, to modify the order or deadlines for designating and deposing experts and the allocation of fees and expenses.
A party may request another party to designate and disclose information concerning testifying expert witnesses only through:
a disclosure request served under Rule 194a.1; or
a deposition or report permitted by this rule.
Unless otherwise ordered by the court, a responding party must provide the information requested under Rule 194a.2(f) by the later of the following dates:
30 days after the date the request is served; or
either, as applicable:
with respect to an expert testifying for a party seeking affirmative relief, 90 days before the end of the discovery period; or
with respect to an expert not described by paragraph (b)(1), 60 days before the end of the discovery period.
A party seeking affirmative relief must make an expert retained by, employed by, or otherwise under the control of the party available for a deposition in accordance with this rule.
If a party seeking affirmative relief does not provide a report of the partys experts factual observations, tests, supporting data, calculations, photographs, and opinions when the party designates the expert, the party must make the expert available for a deposition reasonably promptly after the designation. If the deposition cannot be reasonably concluded more than 15 days before the deadline for designating other experts due to the actions of the party who designated the expert, the court must extend the deadline for other experts
testifying on the same subject.
If a party seeking affirmative relief provides a report of the partys experts factual observations, tests, supporting data, calculations, photographs, and opinions when the party designates the expert, the party is not required to make the expert available for a deposition until reasonably promptly after all other experts have been designated.
A party not seeking affirmative relief must make an expert retained by, employed by, or otherwise under the control of the party available for a deposition reasonably promptly after the party designates the expert and the experts testifying on the same subject for the party seeking affirmative relief have been deposed.
In addition to a disclosure request served under Rule 194a.1, a party may obtain discovery by oral deposition and a report prepared in accordance with Rule 195a.5 of:
the subject matter on which a testifying expert is expected to testify;
the experts mental impressions and opinions;
the facts known to the expert, regardless of when the factual information is acquired, that relate to or form the basis of the experts mental impressions and opinions; and
other discoverable items, including documents not produced in response to a disclosure request.
If the discoverable factual observations, tests, supporting data, calculations, photographs, or opinions of an expert are not recorded and reduced to tangible form, the court may order that information be reduced to tangible form and produced in addition to the deposition.
A partys duty to amend and supplement written discovery regarding a testifying expert is governed by Rule 193.5. If a party retains, employs, or otherwise controls an expert witness, the party must amend or supplement the experts deposition testimony or written report only with regard to the experts mental impressions or opinions and the basis for those impressions or opinions.
When a party takes the oral deposition of an expert witness retained by an opposing party, the party retaining the expert must pay all reasonable fees charged by the expert for time spent in preparing for, giving, reviewing, and correcting the deposition.
Communications between a partys attorney and a testifying expert witness in an action subject to this chapter are protected from discovery regardless of the form of the communications, except to the extent that the communications:
relate to compensation for the experts study or testimony;
identify facts or data that the partys attorney provided and that the expert considered in forming the opinions the expert will express; or
identify assumptions that the partys attorney provided and that the expert relied on in forming the opinions the expert will express.
A draft expert report or draft disclosure required under this rule is protected from discovery regardless of the form in which the draft is recorded.
Notes and Comments: Comment to 1999 change:
Comment to 2021 change: Rule 195 is amended to reflect changes to Rule 194. Amended Rule 195.5(a) lists the disclosures for any testifying expert, which are now required without awaiting a discovery request, that were formerly listed in Rule 194(f). Amended Rule 195.5(a) also includes three new disclosures based on Federal Rule of Civil Procedure 26(a)(2)(B). New Rules 195.5(b) and (c) are based on Federal Rules of Civil Procedure 26(b)(4)(B) and (C) and are added to clarify protections available.
Comment to 2023 change: New Rule 195a is added to implement chapter 301 of the Family Code.