Sued for Patent Infringement: What to Do First

A defendant served with a patent infringement complaint typically has 21 days to respond under Fed. R. Civ. P. 12(a)(1)(A)(i), and the choice of forum, defenses, and timing is governed by the interaction of Rule 12, the patent venue statute at 28 U.S.C. § 1400(b), the local patent rules of the chosen district, and the one-year IPR clock under 35 U.S.C. § 315(b). Each path forecloses some defenses and preserves others; the first-month decisions are strategic, not procedural, and they shape the next two years of the litigation.

Keyhani LLC represents plaintiffs and defendants in patent infringement litigation and broader federal district court IP litigation in the District of New Jersey, the Southern and Eastern Districts of New York, and federal courts nationwide. The decisions a general counsel, CEO, or business owner has to make in the first 30 days of being sued for patent infringement — in the order they actually have to be made — are walked through below, with the governing federal rules and Supreme Court doctrine that constrain each step.

Do Not Communicate with the Patentee Directly

The single most damaging step a defendant’s business team can take in the first week of a patent dispute is calling, emailing, or meeting with the patentee or its counsel without litigation counsel involved. Statements made in those exchanges become exhibits. Casual concessions about how a product works, when it was launched, who designed it, or what the team knew about the asserted patent are routinely cited in willfulness briefing months later, where Halo Electronics, Inc. v. Pulse Electronics, Inc., 579 U.S. 93, 103–04 (2016) ties § 284 enhancement to a discretionary egregiousness standard informed by willfulness — Halo abolished the rigid Seagate test, but enhancement still requires conduct egregious enough to warrant the court’s discretion under § 284, with willfulness as the heartland of that inquiry.

The same rule applies to ignoring the lawsuit. A cease-and-desist letter or complaint cannot be set aside while the engineering team continues to ship the accused product without an internal review. Continued sales after notice, with no documented investigation, are precisely the facts plaintiffs use to argue willful infringement under the Halo standard and to seek attorney fees under Octane Fitness, LLC v. ICON Health & Fitness, Inc., 572 U.S. 545, 554 (2014) (totality-of-the-circumstances “exceptional case” standard under § 285). The two remedies operate independently: Halo‘s willfulness standard governs § 284 enhancement up to three times the damages found, while Octane‘s exceptional-case standard governs § 285 fee-shifting; willfulness alone does not automatically trigger § 285 fees, and a fee award does not depend on willfulness findings.

Preserve Documents and ESI Immediately

The duty to preserve evidence in federal civil litigation attaches when litigation is reasonably anticipated — not when the complaint is served. For a company that has received a cease-and-desist letter or a licensing demand identifying a specific patent, that duty has typically already attached. Routine document destruction policies, automated email purges, and chat-platform retention defaults must be suspended for the relevant custodians and systems on a documented basis.

Fed. R. Civ. P. 37(e) governs the consequences of getting this wrong. Under Rule 37(e), if electronically stored information (ESI) that should have been preserved is lost because a party “failed to take reasonable steps to preserve it,” and it cannot be restored or replaced through additional discovery, the court may order curative measures “no greater than necessary to cure the prejudice.” Where the court further finds that the party acted “with the intent to deprive another party of the information’s use in the litigation,” Rule 37(e)(2) authorizes adverse-inference instructions, dismissal, or default judgment.

Practically, the litigation hold in a patent case has to reach the people who would not normally see one: the founding engineers, departed employees with archived mailboxes, contract manufacturers, the marketing team that wrote the product launch deck, and the cloud-storage administrator who controls retention defaults on Google Workspace, Microsoft 365, Slack, GitHub, or whatever else the company runs. Source-code repositories, build histories, design files, and customer-facing documentation describing how the accused product works are all in scope.

Read the Patent and the Complaint Carefully

Once preservation is in place, the next step is substantive: get the asserted patent and the complaint in front of someone who can actually read them. The complaint will identify the asserted patent (or patents) by number, the specific claims asserted, and at least some of the accused products or product features. The patent itself, retrievable through Google Patents or USPTO Patent Center, contains the claims that define the scope of the alleged exclusive right, the specification that teaches what the invention is, and the prosecution history that may constrain how the claims can be read.

Two questions drive the early read. First, do the asserted claims, on their face, plausibly cover the accused product? Second, is there obvious prior art — a public product, a printed publication, an earlier patent — that predates the asserted patent’s priority date and arguably anticipates or renders obvious the claims under § 102 or § 103? An honest answer to those two questions, however preliminary, frames every later strategic decision. Indefiniteness defenses are governed by Nautilus, Inc. v. Biosig Instruments, Inc., 572 U.S. 898, 901 (2014) (claim is indefinite if it fails to inform skilled artisans about the scope of the invention with reasonable certainty), and warrant their own column in the prior-art and claim-language read.

Software-method claims raise a third question early: is the patent vulnerable under Alice Corp. Pty. Ltd. v. CLS Bank International, 573 U.S. 208 (2014)? The two-step framework articulated in Alice — whether the claims are directed to a patent-ineligible abstract idea, and if so, whether they recite an inventive concept sufficient to transform the claim into a patent-eligible application — has produced a substantial body of motion-to-dismiss decisions invalidating software-method claims at the pleadings stage under § 101. A strong § 101 argument may justify a Rule 12(b)(6) motion before the answer is ever filed.

Evaluate Venue Under TC Heartland

Patent venue is narrower than general federal venue, and after TC Heartland it is meaningfully constrained. The patent venue statute, 28 U.S.C. § 1400(b), provides that any civil action for patent infringement may be brought in the judicial district where the defendant resides, or where the defendant has committed acts of infringement and has a regular and established place of business. In TC Heartland LLC v. Kraft Foods Grp. Brands LLC, 581 U.S. 258, 262 (2017), the Supreme Court held that “[a]s applied to domestic corporations, ‘reside[nce]’ in § 1400(b) refers only to the State of incorporation,” rejecting the broader corporate-residence definition in the general venue statute, 28 U.S.C. § 1391. TC Heartland‘s domestic-corporation rule does not extend to foreign defendants (governed by 28 U.S.C. § 1391(c)(3)) or to LLCs, partnerships, and individuals, each of which carries its own venue analysis.

The Federal Circuit then construed the “regular and established place of business” prong in In re Cray Inc., 871 F.3d 1355 (Fed. Cir. 2017) (requiring a physical, regular, established place of business that is the defendant’s place — employee home offices generally do not qualify). Together, TC Heartland and In re Cray mean a Delaware-incorporated company with all operations in Northern New Jersey is properly sued for patent infringement only in the District of Delaware or the District of New Jersey — not in the Eastern District of Texas, the Western District of Texas, or wherever the patentee finds convenient. A Rule 12(b)(3) motion to dismiss for improper venue, or a 28 U.S.C. § 1404(a) motion to transfer for convenience, is a routine first-month evaluation.

Defendant Profile	Proper Patent Venue	Authority
Domestic corporation, no other ties	State of incorporation only (resides prong)	TC Heartland, 581 U.S. 258 (2017); 28 U.S.C. § 1400(b)
Domestic corporation with physical office in district	State of incorporation, plus any district with regular and established place of business + acts of infringement	28 U.S.C. § 1400(b); In re Cray, 871 F.3d 1355 (Fed. Cir. 2017)
Foreign defendant	Any judicial district where the defendant is subject to personal jurisdiction; TC Heartland‘s residence rule is inapplicable	28 U.S.C. § 1391(c)(3); In re HTC Corp., 889 F.3d 1349 (Fed. Cir. 2018) (post-TC Heartland: alien defendants remain outside § 1400(b) and § 1391’s general venue limits)
Improper venue	Dismissal or transfer under 28 U.S.C. § 1406(a) / Rule 12(b)(3)	Fed. R. Civ. P. 12(b)(3); 28 U.S.C. § 1406(a)

The Decision Tree: Rule 12 Motion or Answer

The 21-day clock under Fed. R. Civ. P. 12(a)(1)(A)(i) can be addressed in three ways: serve an answer, file a Rule 12 motion, or stipulate to an extension. Rule 12(b) lists seven defenses that may be raised by motion before pleading: (1) lack of subject-matter jurisdiction, (2) lack of personal jurisdiction, (3) improper venue, (4) insufficient process, (5) insufficient service of process, (6) failure to state a claim upon which relief can be granted, and (7) failure to join a party under Rule 19. The defenses available against a patent complaint typically reduce to three on this list: improper venue under Rule 12(b)(3), failure to state a claim under Rule 12(b)(6) (often combined with a § 101 patent-eligibility argument), and, less commonly, lack of personal jurisdiction.

A Rule 12 motion does not stay the answer deadline indefinitely. Under Rule 12(a)(4), if the motion is denied or the court postpones disposition until trial, a responsive pleading is due within 14 days after notice of the court’s action, unless the court sets a different time. The choice between motion and answer is rarely binary. Filing a Rule 12(b)(6) motion arguing the asserted claims fail under Alice and § 101 can resolve the case at the pleadings stage in a clean software-patent posture. Filing a Rule 12(b)(3) motion to dismiss for improper venue, or a 28 U.S.C. § 1404(a) motion to transfer to a more convenient forum, can move the case from a forum the patentee selected to one closer to the defendant’s witnesses and documents. Answering immediately, with affirmative defenses and counterclaims for declaratory judgment of noninfringement and invalidity, can signal a willingness to litigate and reset settlement leverage.

Local Patent Rules in D.N.J., SDNY, and EDNY

The Federal Rules set the floor; the local patent rules of the chosen district structure the substantive workflow. In the District of New Jersey, L. Pat. R. 3.1 sets disclosure of asserted claims and infringement contentions at 14 days after the initial scheduling conference; L. Pat. R. 3.6 sets invalidity contentions at 45 days after service of the infringement contentions. L. Pat. R. 4.5(a) requires opening Markman briefs and supporting evidence not later than 45 days after the parties submit their joint claim construction and prehearing statement, with responding briefs due not later than 60 days after the opening submissions under L. Pat. R. 4.5(c) (the standard claim-construction track; design patent and other narrower-record postures use a 30-day responding window). The Southern and Eastern Districts of New York have adopted shared Local Patent Rules whose claim-construction briefing runs on a 30/30/7-day opening/response/reply sequence keyed to a Joint Disputed Claim Terms Chart.

The local-rule cadence matters in two ways. First, a defendant who has not internalized the disclosure deadlines will lose contention amendments to deadlines that ran while the team was still focused on the answer. Second, the rhythm of contentions, claim construction, and the Markman ruling under Markman v. Westview Instruments, Inc., 517 U.S. 370, 372 (1996) (claim construction is a question of law for the court), drives every meaningful settlement window in the case.

Evaluate the Validity Defenses Under Section 282

Validity defenses are the substantive core of most patent defenses. The defenses are codified by subsection at 35 U.S.C. § 282(b). The lead subsections are § 282(b)(1) for noninfringement, § 282(b)(2) for prior-art invalidity (anticipation under § 102, obviousness under § 103), and § 282(b)(3)(A) for any failure of § 112 (the written-description, enablement, and definiteness requirements). Read in full, the four lead subsections cover the universe of typical patent defenses.

§ 282(b)(1) covers “[n]oninfringement, absence of liability for infringement or unenforceability.” § 282(b)(2) reaches “[i]nvalidity of the patent or any claim in suit on any ground specified in part II [of this title] as a condition for patentability,” which incorporates anticipation under § 102 and obviousness under § 103. Courts have read § 282(b)(2) to incorporate § 101 patent-eligibility challenges as well, though the textual fit — whether § 101 is a “condition for patentability” — remains debated. The subsection supporting an indefiniteness defense is § 282(b)(3)(A): it covers “any requirement of § 112, except that the failure to disclose the best mode shall not be a basis on which any claim of a patent may be canceled or held invalid or otherwise unenforceable.” § 282(b)(3)(B) covers “any requirement of § 251” (reissue); and § 282(b)(4) preserves “[a]ny other fact or act made a defense by this title.”

Each ground has its own evidentiary apparatus. Anticipation under § 102 turns on prior public use, sale, publication, or patent — usually proved with public-record evidence assembled during invalidity contentions. Obviousness under § 103, the more common attack, applies the framework of KSR Int’l Co. v. Teleflex Inc., 550 U.S. 398, 415 (2007), which rejected rigid application of the “teaching, suggestion, or motivation” test and instructed courts to apply an “expansive and flexible” obviousness inquiry. Indefiniteness under § 112(b) is governed by Nautilus, 572 U.S. 898, which held that a claim is indefinite if “its claims, read in light of the specification delineating the patent, and the prosecution history, fail to inform, with reasonable certainty, those skilled in the art about the scope of the invention.” In district court, an issued patent enjoys the presumption of validity under § 282(a), and an accused infringer must overcome it by clear and convincing evidence per Microsoft Corp. v. i4i Ltd. P’ship, 564 U.S. 91, 95 (2011).

Decide Whether to File an IPR Petition

IPR at the PTAB is a separate strategic forum that has to be evaluated — not deferred — in the first months of the case. 35 U.S.C. § 315(b) imposes a hard one-year time bar: an IPR “may not be instituted if the petition requesting the proceeding is filed more than 1 year after the date on which the petitioner, real party in interest, or privy of the petitioner is served with a complaint alleging infringement of the patent.” That clock starts on the day the complaint is served and runs for the petitioner, its real parties in interest, and its privies; voluntary dismissal of the underlying suit without prejudice does not reset the clock under Click-to-Call Technologies, LP v. Ingenio, Inc., 899 F.3d 1321 (Fed. Cir. 2018) (en banc as to footnote 3) (voluntary dismissal of underlying suit does not reset the § 315(b) clock). Under Thryv, Inc. v. Click-to-Call Technologies, LP, 590 U.S. 45 (2020), § 314(d) precludes appellate review of the Board’s § 315(b) timeliness determinations — statutory non-reviewability, not Article III jurisdictional vacatur, so the petitioner’s calendar must be right at filing.

A separate, often-overlooked bar at § 315(a)(1) forecloses IPR if the petitioner has previously filed a civil action challenging the validity of any claim of the patent. The classic trap is filing a declaratory-judgment action and then trying to file an IPR; the DJ filing forecloses the IPR even though § 315(a)(3) provides that an invalidity counterclaim “does not constitute a civil action challenging the validity of a claim of a patent for purposes of this subsection.” Joinder under § 315(c) is read narrowly: Facebook, Inc. v. Windy City Innovations, LLC, 973 F.3d 1321, 1336 (Fed. Cir. 2020) limits § 315(c) to joinder of a different party and forecloses same-party “issue joinder” — a petitioner cannot use § 315(c) to add itself as a party to its own already-instituted IPR, and cannot use joinder to add new claims or grounds (including time-barred ones) after the § 315(b) clock has run.

An IPR is a focused validity challenge limited to anticipation and obviousness grounds based on patents and printed publications under § 311(b). Filed strategically, an IPR can produce a stay of the district court action, a Final Written Decision (FWD) invalidating the asserted claims within 12 months of institution under § 316(a)(11), extendable up to 18 months for good cause, and broad estoppel under § 315(e) on grounds the petitioner “raised or reasonably could have raised” — the scope of which was clarified in Cal. Inst. of Tech. v. Broadcom Ltd., 25 F.4th 976, 990–91 (Fed. Cir. 2022) (overruling Shaw Indus. Grp., Inc. v. Automated Creel Sys., Inc., 817 F.3d 1293 (Fed. Cir. 2016)) on the instituted-vs-non-instituted-grounds question and confirming, as to the challenged claims, that the “reasonably could have raised” inquiry sweeps in grounds beyond those the Board instituted.

The discretionary-denial framework under Apple Inc. v. Fintiv, Inc., IPR2020-00019, Paper 11 (PTAB Mar. 20, 2020) (precedential), remains in force as the operative six-factor analysis. What changed is who decides and on what guidance: the February 28, 2025 rescission of the 2022 Vidal memo eliminated the prior bright-line safe harbors, and the October 17, 2025 Squires memorandum (effective October 20, 2025) placed institution decisions with the Director in consultation with at least three PTAB judges. Against that backdrop, a Sotera-style stipulation under Sotera Wireless, Inc. v. Masimo Corp., IPR2020-01019, Paper 12 (PTAB Dec. 1, 2020) (designated precedential as to § II.A Dec. 17, 2020) remains a strong factor against discretionary denial but is no longer a categorical safe harbor.

The decision tree is whether the strongest invalidity grounds are anticipation/obviousness on patents and publications (favoring IPR) or § 112 / § 101 / inequitable conduct (which stay in district court).

Plan for Damages and Injunctive Exposure

Damages exposure is the question business decision-makers ask first. Under 35 U.S.C. § 284, a patentee who proves infringement is entitled to “damages adequate to compensate for the infringement, but in no event less than a reasonable royalty for the use made of the invention by the infringer.” § 284 also permits the court to “increase the damages up to three times the amount found or assessed” — the willfulness enhancement that Halo tied to egregious misconduct under a discretionary standard. Attorney fees under § 285 are governed by Octane‘s totality-of-the-circumstances “exceptional case” standard and operate independently of willfulness; the § 284 and § 285 inquiries are separate.

Injunctive exposure is now narrower than it once was. Under eBay Inc. v. MercExchange, L.L.C., 547 U.S. 388, 391 (2006), a permanent injunction in a patent case requires the plaintiff to demonstrate (1) “that it has suffered an irreparable injury,” (2) “that remedies available at law are inadequate to compensate for that injury,” (3) “that, considering the balance of hardships between the plaintiff and defendant, a remedy in equity is warranted,” and (4) “that the public interest would not be disserved by a permanent injunction.” eBay ended the near-automatic injunction practice that prevailed under earlier Federal Circuit precedent and reduced — though it did not eliminate — the leverage non-practicing entities (NPEs) can exert through injunction threats. Operating-company plaintiffs who actually compete with the defendant remain better positioned to satisfy the four-factor test than NPEs are.

Per-Side Perspective: Defendant vs. Patent Owner

Map the Litigation Timeline

A patent infringement lawsuit in federal district court typically runs 18 to 36 months from complaint to trial, with appellate review to the Federal Circuit thereafter. The variance is real: the District of Delaware moves faster than many forums, the Eastern and Western Districts of Texas have specific patent procedures, and the District of New Jersey and the Southern and Eastern Districts of New York operate under local patent rules that structure each phase on a defined schedule.

The high-level path runs through pleadings (months 1–3), infringement and invalidity contentions (months 3–6), claim-construction discovery and Markman briefing (months 6–12), fact discovery (months 6–15), expert discovery (months 12–18), summary judgment (months 15–20), and trial (months 20–30). An IPR filed in months 3–6, if instituted, often runs to a Final Written Decision in months 18–24 — sometimes ahead of trial, sometimes during it. Settlement windows open at every transition: after the answer, after Markman, after invalidity contentions are exchanged, and on the eve of summary judgment.

Cost Drivers in Patent Litigation

Patent litigation costs vary by case complexity, technology, forum, and the number of asserted patents and claims. Cost drivers that have outsized effects include the number of asserted claims that proceed to claim construction, the volume of source-code and ESI in discovery, the number of expert witnesses required (technical and damages), whether an IPR is filed in parallel, and whether the case proceeds to trial or resolves at summary judgment or in mediation. The American Intellectual Property Law Association’s biennial Report of the Economic Survey publishes per-case median cost ranges by amount-in-controversy bands, and the Lex Machina patent litigation analytics platform tracks forum-by-forum trial rates, time-to-trial, and outcome distributions; counsel typically use both data sources in early budgeting. To discuss budget and forum-specific cost expectations for a particular matter, contact Keyhani LLC.

Why Keyhani LLC for Patent Infringement Defense

Keyhani LLC represents plaintiffs and defendants in federal patent litigation in the District of New Jersey, the Southern and Eastern Districts of New York, and (pro hac vice) federal courts nationwide, and advises on parallel PTAB strategy and Federal Circuit appeals from PTAB decisions. The firm is an intellectual property litigation boutique handling defense-side and plaintiff-side patent matters from cease-and-desist response through Markman, summary judgment, trial, and appeal.

Darius Keyhani is admitted to the bars of the District of Columbia, New Jersey, the U.S. Court of Appeals for the Federal Circuit, the U.S. Supreme Court, and the Southern, Eastern, and Western Districts of New York, and holds an LL.M. from NYU School of Law. The firm regularly handles defense-side patent litigation from cease-and-desist response and complaint analysis through Markman, summary judgment, trial, and appeal — including venue and 28 U.S.C. § 1404(a) transfer practice, IPR-timing and parallel-PTAB advisory strategy, Federal Circuit appeals from PTAB decisions, and the § 282 validity defenses that drive substantive disposition of most patent cases.

Frequently Asked Questions About Being Sued for Patent Infringement