Guides · Patent Litigation
Discovery in Patent Cases
Discovery is usually the most expensive phase of a patent case.
· Law checked through October 20, 2026
In Short
Discovery is usually the most expensive phase of a patent case. It centers on how the accused products work (often source code), how the invention was developed and prosecuted, what the parties knew about each other, and the financial data behind damages. Courts in Texas manage cost with model orders that limit email discovery and with protective orders that restrict who may see confidential technical material.
Common situations.
- A defendant must make its source code available to the patent owner's experts.
- A patent owner asks for every email that mentions the patent.
- An in-house lawyer who also prosecutes patents wants access to the other side's technical documents.
- A company that relied on an opinion of counsel wonders what privilege it has given up.
What gets exchanged.
| Topic | Typical discovery |
|---|---|
| Infringement | Technical documents, schematics, source code, product samples, testing |
| Validity | Prior art, the inventors' files, conception and development records, early sales and offers |
| Prosecution | The file history, related applications, communications with the patent office |
| Knowledge and willfulness | When each side learned of the patent, notice letters, opinions of counsel relied on |
| Damages | Unit sales, revenue, costs, profits, licenses and settlement agreements, marking practices, market studies |
Discovery must be relevant to a claim or defense and proportional to the needs of the case (Fed. R. Civ. P. 26(b)(1)).
Limits on email and electronic discovery.
The Eastern District of Texas's model e-discovery order for patent cases (Gen. Order 14-6, Mar. 19, 2014):
- excludes email from general document requests; email must be sought through specific requests served after core disclosures and contentions;
- limits each requesting party to 8 custodians per producing party and 10 search terms per custodian, unless the parties agree or the court orders otherwise;
- excludes most metadata absent good cause.
The Waco standing order used in the Western District (OGP 4.0) similarly does not require general email production absent good cause.
Protective orders and source code.
Patent cases almost always proceed under a protective order with tiers of confidentiality. Highly confidential technical material, especially source code, is usually made available only on a stand-alone computer at a secure location, with limits on printing.
Many protective orders also include a prosecution bar, which prevents anyone who reviews the other side's technical secrets from prosecuting patents in the same field for a period. Whether a particular lawyer is barred depends on whether that lawyer is involved in competitive decision-making, such as drafting or amending claims (In re Deutsche Bank Tr. Co. Ams., 605 F.3d 1373 (Fed. Cir. 2010)).
Privilege.
- Opinions of counsel. A defendant that relies on an opinion of counsel to defend against willfulness waives privilege over communications on the same subject (In re EchoStar Commc'ns Corp., 448 F.3d 1294 (Fed. Cir. 2006)). The waiver generally does not reach trial counsel (In re Seagate Tech., LLC, 497 F.3d 1360 (Fed. Cir. 2007) (en banc)).
- Patent agents. Communications with a registered patent agent about matters within the agent's authorized practice before the Patent Office are privileged (In re Queen's Univ. at Kingston, 820 F.3d 1287 (Fed. Cir. 2016)).
- Experts. Draft expert reports and most communications between counsel and testifying experts are protected (Fed. R. Civ. P. 26(b)(4)(B), (C)).
Discovery from abroad.
When witnesses or documents are overseas, parties may need to use the Hague Evidence Convention or letters rogatory, which can take months. In the other direction, a party to a foreign proceeding may ask a U.S. district court to order discovery from a person in its district for use abroad (28 U.S.C. § 1782).
Texas notes.
- Eastern District of Texas. The court's standard discovery order requires parties to produce documents relevant to the claims and defenses without waiting for formal requests. Discovery begins early, alongside infringement and invalidity contentions. See Local Patent Rules in Texas Federal Courts.
- Western District of Texas. Under OGP 4.0, discovery other than venue, jurisdiction, and claim construction discovery was stayed until after the claim construction hearing, with set limits on interrogatories, requests, and deposition hours afterward. Confirm the current practice of the assigned judge.
- Litigation funding. Courts differ on whether funding agreements are discoverable. The Northern District of Texas requires disclosure of all persons financially interested in the outcome in the certificate of interested persons.
Sources.
- Fed. R. Civ. P. 26(b)(1), 26(b)(4).
- 28 U.S.C. § 1782.
- E.D. Tex. General Order 14-6, Model Order Regarding E-Discovery in Patent Cases (Mar. 19, 2014).
- W.D. Tex. Standing Order Governing Proceedings (OGP) 4.0, Patent Cases (Mar. 7, 2022).
- N.D. Tex. L.R. 3.1(c), 3.2(e).
- In re Deutsche Bank Tr. Co. Ams., 605 F.3d 1373 (Fed. Cir. 2010).
- In re EchoStar Commc'ns Corp., 448 F.3d 1294 (Fed. Cir. 2006).
- In re Seagate Tech., LLC, 497 F.3d 1360 (Fed. Cir. 2007) (en banc).
- In re Queen's Univ. at Kingston, 820 F.3d 1287 (Fed. Cir. 2016).
This guide is general information, not legal advice. Law checked through October 20, 2026. See the Disclaimer.