Patent litigation is the federal court process for resolving disputes over patent rights, most often when a patent owner sues someone for making, using, selling, or importing a patented invention without permission. These cases can also test whether the patent should have been granted at all. They are slow, technically dense, and expensive: most run two to three years before trial, and median costs climb into the hundreds of thousands or millions of dollars depending on what is at stake. The basic shape of the process is the same whether you own the patent, have been accused of infringing one, or are weighing the risk of either.
What Patent Infringement Means
A U.S. patent gives its owner the right to stop others from making, using, selling, or importing the patented invention for a term that generally runs 20 years from the filing date of the application.1Office of the Law Revision Counsel. 35 U.S. Code 154 – Contents and Term of Patent; Provisional Rights Doing any of those things during that term without the owner’s authorization is direct infringement.2Office of the Law Revision Counsel. 35 U.S. Code 271 – Infringement of Patent
Copying isn’t required. If a product or process falls within the scope of the patent’s claims, it infringes, even if the accused infringer developed it independently and had never heard of the patent.
The law also recognizes two forms of indirect infringement. Inducement is encouraging or instructing someone else to infringe. Contributory infringement is selling a component that has no real use outside the patented invention, knowing it will be used to infringe.2Office of the Law Revision Counsel. 35 U.S. Code 271 – Infringement of Patent Both require proof of knowledge, which makes them harder to establish than direct infringement.
Where These Cases Are Filed
Patent cases belong in federal court. Federal district courts have exclusive jurisdiction over patent disputes, and state courts cannot hear them.3Office of the Law Revision Counsel. 28 U.S. Code 1338 – Patents, Plant Variety Protection, Copyrights, Mask Works, Designs, Trademarks, and Unfair Competition
The patent owner also can’t pick any federal courthouse. A patent case can only be filed in a district where the defendant resides, or where the defendant has committed acts of infringement and has a regular and established place of business.4Office of the Law Revision Counsel. 28 U.S. Code 1400 – Patents and Copyrights, Mask Works, and Designs Venue matters. Certain districts have reputations for faster timelines, more experienced patent judges, or local rules that tilt in a particular direction. The Western District of Texas and the District of Delaware consistently rank among the busiest patent courts in the country, and choosing where to file is one of the first strategic decisions in a case.
How a Patent Lawsuit Moves Through Court
A patent case follows the general shape of federal civil litigation, with a few steps that exist only in patent law. Most reach trial two to three years after filing, though many resolve earlier through settlement or motions.
Filing and Response
The patent owner files a complaint identifying the patent, accusing the defendant of infringement, and stating what relief it wants. The defendant answers, usually denying infringement and raising defenses and counterclaims, almost always including a challenge to the patent’s validity.
Discovery
Both sides exchange evidence: internal documents, written questions called interrogatories, and depositions where witnesses answer under oath. Patent discovery is notoriously expensive because it often sweeps in massive volumes of technical documents, source code, and engineering records. Each side also hires expert witnesses to opine on infringement, validity, and damages.
Claim Construction (the Markman Hearing)
This step is unique to patent litigation and often decides the case. Patent claims are written in precise technical language, and the parties almost always disagree about what key terms mean. At a Markman hearing, the judge interprets the disputed claim terms and sets the legal boundaries of the patent. It’s a question of law, so the judge decides it, not a jury. Because the meaning of a single word can determine whether an accused product infringes, many cases settle in the weeks after the Markman ruling comes down.
Summary Judgment and Trial
After claim construction, parties often move for summary judgment, asking the court to rule in their favor without a trial. If those motions fail and the case doesn’t settle, it goes to trial. A jury (or in some cases the judge alone) decides whether infringement occurred, whether the patent is valid, and what damages the patent owner is owed.
What Defendants Usually Argue
Few defendants simply deny that anything happened. Most defenses stack several arguments, and the strongest ones attack the patent itself rather than only the accused conduct.
- Non-infringement. The accused product or process does not fall within the patent claims as the court construed them.
- Invalidity. The patent should never have issued, usually because the invention wasn’t novel (prior art already existed) or was an obvious step given what was already known. Every patent is presumed valid, and the defendant must prove invalidity by clear and convincing evidence, a higher bar than the usual civil standard. Even so, invalidity attacks succeed often enough to be a routine feature of nearly every case.5Office of the Law Revision Counsel. 35 U.S. Code 282 – Presumption of Validity; Defenses
- Equitable estoppel. The patent owner’s own conduct led the defendant to reasonably believe no suit was coming, and the defendant actually relied on that conduct when it decided to go ahead.
- Patent exhaustion. Once the patent owner sells a patented unit, its rights over that specific unit are exhausted, and the buyer can use or resell it without infringing.
What the Patent Owner Can Win
A win can be expensive for the losing side. Federal law guarantees damages of at least a reasonable royalty for the infringer’s use of the invention.6Office of the Law Revision Counsel. 35 U.S. Code 284 – Damages That is the floor.
A reasonable royalty is what the parties would hypothetically have agreed to in a licensing negotiation just before the infringement began. Courts look at existing licenses, the patent’s importance to the product, and the profitability of the infringing sales. When the patent owner can prove it lost actual sales because of the infringement, it can recover lost profits instead, which often produces a much larger award.6Office of the Law Revision Counsel. 35 U.S. Code 284 – Damages
Damages can be tripled when the infringer’s conduct was egregious. The Supreme Court has said enhanced damages should generally be reserved for willful misconduct, but district courts have broad discretion to weigh the circumstances and don’t need to find the infringement objectively reckless.7Justia U.S. Supreme Court. Halo Electronics, Inc. v. Pulse Electronics, Inc., 579 U.S. ___ (2016) The classic trigger is copying after being put on notice of the patent.
Money is not the only remedy. A court can order the infringer to stop the infringing activity entirely.8Office of the Law Revision Counsel. 35 U.S. Code 283 – Injunction Injunctions are not automatic even after a finding of infringement. The Supreme Court requires the patent owner to show irreparable harm, that money damages are inadequate, that the balance of hardships favors an injunction, and that the public interest would not be disserved.9Justia U.S. Supreme Court. eBay Inc. v. MercExchange, L.L.C., 547 U.S. 388 (2006) Patent owners who don’t practice the invention themselves, including some licensing entities, often struggle to meet this test.
In exceptional cases, the court can award reasonable attorney fees to the prevailing side.10Office of the Law Revision Counsel. 35 U.S. Code 285 – Attorney Fees It cuts both ways. A patent owner who brings a frivolous case can be stuck with the defendant’s legal bills; an infringer who litigates in bad faith can owe the patent owner’s fees on top of damages.
Marking Rules and the Six-Year Damages Cap
Patent owners who sell products covered by their patent need to pay attention to marking, because failure to mark can sharply limit what they recover. If you sell a patented product without marking it with the patent number (or a web address linking the product to the number), you generally cannot recover damages for infringement that happened before you gave the infringer actual notice. Filing the lawsuit counts as notice, but infringement before that date may be unrecoverable.11Office of the Law Revision Counsel. 35 U.S. Code 287 – Limitation on Damages and Other Remedies; Marking and Notice
Separately, damages have a hard time limit regardless of marking. You cannot recover for any infringement that occurred more than six years before the complaint was filed.12Office of the Law Revision Counsel. 35 U.S. Code 286 – Time Limitation on Damages This isn’t a statute of limitations that kills the suit; you can still file and seek an injunction. It caps how far back your monetary recovery goes.
Inter Partes Review as a Parallel Track
Not every patent dispute has to be fought in a courtroom. Inter partes review (IPR) is a proceeding before the Patent Trial and Appeal Board, an administrative body inside the U.S. Patent and Trademark Office, where a challenger can ask the Board to cancel patent claims as unpatentable over prior patents and printed publications.13Office of the Law Revision Counsel. 35 U.S. Code 311 – Inter Partes Review
Anyone who does not own the patent can file an IPR petition.14United States Patent and Trademark Office. Inter Partes Review The Board institutes the proceeding only if the petitioner shows a reasonable likelihood of prevailing on at least one challenged claim. Once instituted, the Board must issue a final decision within one year, extendable by up to six months for good cause.15Office of the Law Revision Counsel. 35 U.S. Code 316 – Conduct of Inter Partes Review
IPR is faster and cheaper than full district court litigation, which is why defendants frequently file an IPR petition while they defend the lawsuit in court. Two limits to know. IPR addresses validity only, not infringement, so if the patent survives, the court case continues. And a petitioner is barred from raising in court any invalidity ground it raised or reasonably could have raised in the IPR.
Settlement, Appeals, and What It Costs
The great majority of patent cases settle before trial. The expense and uncertainty of going the distance are too high for most parties, and a negotiated resolution usually makes more business sense. Settlements often take the form of a going-forward license with royalties, a lump-sum payment, or a cross-license in which both sides grant each other rights to their respective patents.
When a case does reach judgment, either side can appeal to the U.S. Court of Appeals for the Federal Circuit, which has exclusive jurisdiction over patent appeals from district courts.16Office of the Law Revision Counsel. 28 U.S. Code 1295 – Jurisdiction of the United States Court of Appeals for the Federal Circuit The Federal Circuit reviews claim construction and other legal issues without deference to the trial court, so Markman rulings can be overturned on appeal. Jury findings on infringement and damages get more deferential review. An appeal typically adds a year or more.
Patent litigation is among the most expensive civil litigation there is. Industry surveys put median costs through trial at roughly $600,000 when less than $1 million is at stake, rising above $3.5 million when more than $25 million is on the line. Even reaching the end of discovery and claim construction, without trial, can run $300,000 to $1.5 million depending on complexity and amount in dispute. IPR proceedings, by comparison, usually wrap up 12 to 18 months after institution. Those numbers go a long way toward explaining why settlement is the rule and trial the exception.