CROSSOVER: Mandamus Reins In Discovery Order: No Waiver of Attorney-Client Privilege by Partial Disclosure or Mere Use of Legal Advice

In re EOG Resources, Inc., 04-25-00574-CV, April 15, 2026.

On appeal from Probate Court No. 3, Bexar County, Texas

Synopsis

The Fourth Court of Appeals conditionally granted mandamus and held that EOG did not waive attorney-client privilege merely by producing a redacted legal memorandum and an internal email that referenced counsel’s advice on the same subject. The court also rejected offensive-use waiver because EOG was a defendant asserting only defenses, not seeking affirmative relief independent of the plaintiff’s claims.

Relevance to Family Law

This opinion matters in Texas family litigation because privilege-waiver fights frequently arise in divorce, SAPCR, enforcement, fiduciary-duty, and marital-property tracing cases, especially where one side has consulted transactional, tax, estate, business, or family-law counsel about asset structure, title, valuation, reimbursement, or litigation strategy. In re EOG Resources gives family-law litigators a strong mandamus-ready framework for arguing that partial disclosure, subject-matter overlap, or a client’s reliance on legal advice in decision-making does not automatically open the file—and that offensive-use waiver remains narrow when the party is defending rather than pursuing affirmative relief.

Case Summary

Fact Summary

The underlying dispute involved title to mineral interests and related royalty rights in long-running probate litigation. One unresolved issue was whether EOG acquired certain mineral interests as a bona fide purchaser. In discovery, the opposing party sought documents bearing on that issue, and EOG withheld several items—identified as title opinions, attorney memoranda, and attorney-client communications—on attorney-client privilege grounds.

To support the privilege claim, EOG did what Texas mandamus practice expects: it served a detailed privilege log, submitted affidavits from corporate representatives explaining the nature of the communications, and tendered the disputed documents for in camera inspection. The trial court nevertheless ordered production of five withheld items after concluding that EOG had waived privilege.

The waiver theory rested primarily on EOG’s prior voluntary production of a redacted 2013 legal memorandum from its title attorney and an October 2013 internal email stating that EOG’s title attorney had advised that an amended correction mineral deed was needed. The real party in interest argued that because those disclosed materials addressed the same title problem as the withheld documents, privilege had been waived as to the withheld communications. It also argued offensive-use waiver. EOG sought mandamus.

Issues Decided

• Whether EOG established a prima facie claim of attorney-client privilege as to the withheld documents.
• Whether voluntary disclosure of a redacted legal memorandum and an internal email referencing legal advice waived privilege under Texas Rule of Evidence 511(a)(1).
• Whether disclosure of communications on the same general subject matter, or mere use of legal advice, constitutes waiver.
• Whether offensive-use waiver applied where EOG was a defendant asserting only defenses.
• Whether mandamus was the proper remedy for the discovery order compelling production of privileged material.

Rules Applied

The court relied on familiar Texas privilege and mandamus doctrine:

• Texas Rule of Evidence 503 protects confidential communications between attorney and client made to facilitate legal services.
• A party asserting privilege must establish a prima facie case, which can be done through a privilege log and supporting affidavits. The court cited In re Christus Santa Rosa Health System, 492 S.W.3d 276, 279 (Tex. 2016), and Jordan v. Court of Appeals, 701 S.W.2d 644, 648–49 (Tex. 1985).
• Under Texas Rule of Evidence 511(a)(1), waiver by disclosure occurs only if the privilege holder voluntarily discloses a “significant part of the privileged matter.”
• The court leaned heavily on the Texas Supreme Court’s modern narrowing of subject-matter waiver principles. Citing In re Richardson Motorsports, Ltd., 690 S.W.3d 42, 58 (Tex. 2024), and University of Texas System v. Franklin Center for Government & Public Integrity, 675 S.W.3d 273, 288 (Tex. 2023), the court emphasized that disclosure of the same subject matter does not waive privilege unless the disclosure quotes from or unambiguously refers to and describes a significant part of the privileged communication itself.
• The court also reiterated that use of privileged information is not necessarily waiver, citing Republic Insurance Co. v. Davis, 856 S.W.2d 158, 163 (Tex. 1993), and its own prior reasoning in In re Patricia A. Mansell.
• For offensive-use waiver, the court applied Republic Insurance, General Land Office v. Oxy U.S.A., Inc., 789 S.W.2d 569, 570 (Tex. 1990), and BHP Petroleum Co. v. Millard, 800 S.W.2d 838, 841 (Tex. 1990): the privilege holder must be seeking affirmative relief, the privileged information must probably determine the outcome, and the evidence must be otherwise unavailable.
• On mandamus, the court followed Walker v. Packer, 827 S.W.2d 833, 843 (Tex. 1992), and In re Prudential Insurance Co. of America, 148 S.W.3d 124, 135–36 (Tex. 2004): compelled disclosure of privileged matter is a classic situation where appellate remedy is inadequate.

Application

The court began with the threshold question and found EOG had properly carried its prima facie burden. The privilege log was detailed, the supporting affidavits explained the privileged character of the documents, and the documents themselves were tendered for in camera review. That shifted the burden to the party claiming waiver.

From there, the court rejected the voluntary-disclosure theory because the disclosed materials did not reveal a significant part of the withheld communications. The redacted 2013 memorandum discussed the deed problem and gave legal advice about obtaining an amended correction mineral deed, but the court found that memorandum neither depended upon the content of the withheld items nor quoted from or revealed a significant part of them. The same was true of the October 2013 internal email. The email said counsel had advised that an amended correction deed was needed, but it did not disclose the underlying attorney-client communications in any meaningful way.

The court’s reasoning is strategically important: it treated “same subject matter” and “reference to legal advice” as insufficient by themselves. In other words, a party does not lose privilege simply because it discloses one attorney communication, a redacted portion of one communication, or an internal email reflecting that legal advice was received and acted upon. The focus remains on whether the disclosure exposed a significant part of the withheld privileged communication itself.

The court then rejected offensive-use waiver for a simpler reason: EOG was a defendant asserting defenses only. It was not seeking affirmative relief independent of the plaintiff’s claims. Because the first element of offensive-use waiver failed, the doctrine did not apply. Having found the documents privileged and not waived, the court held the trial court abused its discretion. And because disclosure of privileged information cannot be un-done on appeal, mandamus relief was appropriate.

Holding

The Fourth Court held that EOG established a prima facie claim of attorney-client privilege as to the disputed title opinions, attorney memoranda, and attorney communications through its privilege log, supporting affidavits, and in camera submission. That showing was sufficient to shift the burden to the party asserting waiver.

The court further held that EOG did not waive privilege under Rule 511(a)(1) by producing a redacted 2013 legal memorandum and an internal email referring to counsel’s advice. Those materials did not quote from, describe, or reveal a significant part of the withheld privileged communications, and disclosure of the same subject matter or mere use of legal advice does not constitute waiver.

The court also held that offensive-use waiver did not apply because EOG was not seeking affirmative relief. As a defendant asserting defenses only, it remained outside the narrow scope of that doctrine.

Finally, the court held that mandamus was proper because an order compelling production of privileged material leaves no adequate appellate remedy. The petition was conditionally granted, and the trial court was directed to vacate the production order as to the disputed privilege-log items.

Practical Application

For family-law litigators, this case is most useful in high-conflict discovery involving separate-property tracing, business-entity ownership, estate-planning structures, post-marital partition agreements, reimbursement theories, valuation strategy, and custody matters where one side consulted counsel before acting. Opposing counsel often argues waiver after obtaining a single disclosed email, a redacted memo, a draft agreement with lawyer comments removed, or testimony that a client “acted on advice of counsel.” In re EOG Resources is a clean answer: disclosure of the topic is not disclosure of a significant part of the privileged communication.

In property litigation, this comes up when a spouse produces a redacted estate-planning memo, business-sale document, or title analysis touching the same asset at issue in divorce. The producing party can now more forcefully argue that the remainder of counsel’s file stays protected unless the disclosed material actually reveals the substance of the withheld communications. In fiduciary-duty or fraud-adjacent claims between spouses, the same principle should limit attempts to bootstrap a partial production into a broad subject-matter waiver.

The case is also important defensively. Family lawyers should be careful when framing pleadings and live positions so that defenses stay defensive. If your client is only resisting characterization, valuation, reimbursement, conservatorship restrictions, relocation, or fee claims, EOG helps argue there is no offensive-use waiver merely because your client’s theory is informed by legal advice. But if you plead affirmative claims—fraud on the community, rescission, declaratory relief, partition enforcement, fiduciary-duty recovery, reimbursement, or sanctions-based affirmative relief—you should expect a more serious offensive-use fight.

Practically, this opinion reinforces three habits: build the privilege record, disclose surgically, and separate “we received legal advice” from “here is what counsel said.” The more disciplined the record, the better the mandamus posture.

Checklists

Building the Privilege Record

• Serve a detailed privilege log identifying date, author, recipients, capacities, and privilege basis.
• Use affidavits from a client representative or attorney to explain the purpose of the communication and why it was made to facilitate legal services.
• Distinguish legal advice from business, accounting, co-parenting, or operational communications.
• Tender disputed documents for in camera review when necessary.
• Preserve a clean record at the hearing showing exactly which documents remain disputed.

Avoiding Waiver by Partial Production

• Redact narrowly and intentionally; disclose only what is necessary.
• Before producing a memo or email, ask whether the excerpt quotes, summarizes, or reveals a significant part of other privileged communications.
• Avoid internal emails that paraphrase counsel’s legal analysis in detail.
• Where possible, describe the fact of advice without disclosing the substance of the legal reasoning.
• Accompany sensitive productions with a written reservation of privilege as to withheld portions and related communications.

Responding to Waiver Arguments in Family Cases

• Frame the dispute around Rule 511(a)(1): no waiver absent disclosure of a significant part of the privileged matter.
• Emphasize that same-subject-matter overlap is not enough.
• Compare the disclosed document line-by-line against the withheld materials if necessary.
• Argue that testimony or evidence showing a party acted after consulting counsel does not itself disclose the privileged communication.
• Remind the trial court that compelled disclosure of privileged material is mandamus-sensitive and effectively unreviewable after production.

Defeating Offensive-Use Waiver

• Analyze whether your client is actually seeking affirmative relief or merely asserting defenses.
• If defending only, make that explicit in briefing and at the hearing.
• Avoid unnecessarily pleading standalone claims that could transform a defensive posture into an affirmative one.
• If affirmative relief is pleaded, evaluate whether privileged information is truly outcome-determinative and otherwise unavailable.
• Separate factual defenses from any suggestion that the client’s entitlement depends on proving the content of counsel’s advice.

Using the Case Against Overreaching Discovery Requests

• Object when the opposing party equates “reference to advice” with waiver.
• Resist broad requests for “all communications on the same subject.”
• Ask the court to review the exact disclosed language rather than generalized accusations of selective disclosure.
• Press the requesting party to identify the specific “significant part” allegedly revealed.
• Be prepared to seek mandamus promptly if the trial court orders production of privileged material.

Preventing the Non-Prevailing Party’s Mistake

• Do not rely on broad subject-matter waiver rhetoric untethered to actual disclosed language.
• Do not assume an internal email mentioning counsel’s recommendation opens the entire lawyer file.
• Do not invoke offensive-use waiver unless the opposing party is truly seeking affirmative relief independent of your claims.
• Do not underdevelop the record on whether the evidence is otherwise unavailable.
• Do not ask the trial court to collapse “use of legal advice” into “waiver of legal advice.”

Citation

In re EOG Resources, Inc., No. 04-25-00574-CV, 2026 WL ___ (Tex. App.—San Antonio Apr. 15, 2026, orig. proceeding) (mem. op.).

Full Opinion

Read the full opinion here

Family Law Crossover

This ruling can be weaponized effectively in Texas divorce and custody cases in at least two directions. First, for the privilege holder, it is a strong shield against efforts to pry into communications with family-law counsel, estate planners, tax lawyers, business lawyers, or prior counsel simply because the client produced a redacted draft, disclosed a timeline showing counsel was consulted, or testified that a decision was made after legal review. That is especially useful in disputes over separate-property origin, entity control, trust interests, post-marital agreements, relocation decisions, child-related risk management, and pre-suit strategy.

Second, for the requesting party, the case teaches precision. If you want privileged material, you will need to do more than show that the other side disclosed a related communication or invoked legal advice as part of the narrative. You must identify how the disclosure revealed a significant part of the withheld communication itself, or show that the other side has crossed into true offensive use by seeking affirmative relief that depends on the privileged material. In practice, In re EOG Resources narrows casual waiver arguments and rewards litigators who build a disciplined record, distinguish claims from defenses, and target the actual content of the disclosure rather than the topic alone.

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