Defenses to Patent Infringement

There are several defenses to patent infringement, which are important for patent holders to understand the strengths of their case and for the accused to use as a shield. Generally, in patent infringement litigation, patents are presumed to be valid, and defendants bear the burden of proving that the patent is either invalid or not infringed. Defendants may also use other equitable and other affirmative defenses against allegations of patent infringement.

A. Invalidity

Defendants can attack the validity of the patent by arguing that the U.S. Patent and Trademark Office incorrectly issued the patent. The defendant must prove that the elements for obtaining a patent, most commonly the non-obviousness or novelty requirements, were not satisfied. The defendant can also argue invalidity if it can prove that the plaintiff engaged in inequitable conduct such as by withholding information that the examiner should have known about or lying to the examiner.

B. Non-Infringement

Patent infringement occurs when a party sells, manufactures, or uses a patented invention without the authorization of the patent owner. There are several types of infringement- direct or literal infringement, infringement by inducement, or contributory infringement. Even if the patent was validly issued, a defendant may argue that its product did not infringe. To successfully argue non-infringement, generally the defendant will distinguish its invention from plaintiff's patent claims. This is sometimes referred to as the accused product not "reading on the claims" of the asserted patent.

C. First Sale Doctrine

Patent law only protects the original sale of an invention, thereafter it is deemed "exhausted." Secondary markets legally exist since patents do not prevent purchasers from reselling the item they purchased. However, the plaintiff has two rebuttals to this defense. First, if the plaintiff did not authorize the initial sale, this defense is invalid. Second, if the initial sale was of an infringing invention, reselling that infringing invention does not cure the infringement.

D. Misuse

In order to deter inventors from breaking the law or engaging in unethical activity, a plaintiff who does so for the benefit of its patents will be barred from bringing successful infringement claims. For example, an inventor who bribes a government official to decrease competition or other favorable treatment would not be able to successfully sue someone for infringing that patent.

E. Repair Doctrine

The repair doctrine says it is not infringement to repair a patented invention or to replace unpatented components in patented inventions. If this rule did not exist, repairmen would live in constant fear of getting sued, and society would generate much more waste. However, a defendant who completely rebuilds a patented invention or repairs an infringing invention will not be able to rely on this defense.

F. Estoppel

Estoppel is an equitable concept that allows a defendant to rely on written representations of the plaintiff. For example, if the plaintiff wrote defendant to inform defendant it has no plans on bringing a lawsuit against the defendant, and as a result of that letter, defendant spent a lot of money increasing its production and inventory, the plaintiff will not be able to change its mind. In the patent context, it is much more likely that the plaintiff will be estopped as a result of its conversations with the patent examiner with respect to the limitations of the invention or disclaiming any rights to the invention.

G. Statute of Limitations or Laches

The Lanham Act does not allow a plaintiff to recover money damages incurred more than six years prior to filing the lawsuit. This, and the related equitable doctrine of laches (which will bar a defendant from obtaining an injunction and other non-monetary damages if it unreasonably delays in bringing a lawsuit) both deter plaintiffs from sitting on their hands and then reaping the benefits of the defendant spending time and efforts on the infringing product.

If you need assistance because you are facing a patent infringement lawsuit or believe someone is infringing your patent, call the Law Offices of Roland Tong, at 949-298-6867 or email Mr. Tong at roland@rtlawoffices.com. Mr. Tong has been obtaining patent, trademark, and copyright protections for his clients since 2001. He has represented a wide range of clients from start-up companies to Fortune 500 companies in a wide range of industries.