Section 282 of the Patent Act provides for the following defenses: (1) noninfringement, absence of liability for infringement or unenforceability; (2) patent invalidity; and (3) any other fact or act made a defense.
10.5.3.1 Patent invalidity
Section 282(a) of the Patent Act provides that patents “shall be presumed valid.” Therefore, the patent owner does not need to prove validity in an infringement action. The challenger bears the burden to prove invalidity by “clear and convincing evidence.”118
10.5.3.2 Other defenses
An alleged infringer can defend on the ground that the patentee has consented to their use of the technology by, for example, granting a license.
Under the first-sale doctrine (sometimes referred to as the exhaustion principle), a form of implied license by operation of law, the first unrestricted sale of a patented product exhausts the patentee’s control over that product, and it can be resold and repaired without implicating the patent owner’s rights.119 The line between permitted repair and impermissible reconstruction is not easily determined, resulting in rather vague, context-specific rulings.120 Such issues arise frequently in the context of contributory infringement claims, where the alleged infringer is providing specialized replacement parts.
Courts have long recognized a common-law defense of experimental use. The Federal Circuit has, however, interpreted this doctrine quite narrowly, limiting it to uses “for amusement, to satisfy idle curiosity, or for strictly philosophical inquiry.”121 In addition to the common-law doctrine of experimental use, § 271(e) creates a limited experimental use exception for submitting information for regulatory purposes.
Section 273 of the Patent Act provides for a prior-use right to a defendant who commercially used the invention in the United States at least one year before the earlier of either (1) the effective filing date or (2) the date of the first public disclosure of the claimed invention. The prior-use defense must be established by clear and convincing evidence.
Even where a defendant cannot prove that the patent has not been infringed or is invalid, it may avoid liability by showing that the patentee engaged in inequitable conduct or patent misuse or by proving another equitable defense (equitable estoppel or prosecution laches). Inequitable conduct may “arise from an affirmative misrepresentation of a material fact, failure to disclose material information, or submission of false material information, coupled with an intent to deceive or mislead the [US]PTO.”122 A determination that inequitable conduct occurred in relation to one or more claims will render the entire patent unenforceable.123
Inequitable conduct claims must be pled with particularity under FRCP 9(b), and these claims “require identification of the specific who, what, when, where, and how of the material misrepresentation or omission committed before the [US]PTO.”124 The accused infringer must prove both materiality and intent by clear and convincing evidence.125 Once these threshold findings are established, the court “must weigh them to determine whether the equities warrant a conclusion that inequitable conduct occurred.”126 “Intent and materiality are separate requirements. A district court should not use a ‘sliding scale,’ where a weak showing of intent may be found sufficient based on a strong showing of materiality and vice versa.”127
The affirmative defense of patent misuse exists to prevent harm to the market caused by a patentee extending a patent’s right to exclude beyond its legal scope.128 The underlying principle of misuse is that an alleged infringer must prove by clear and convincing evidence that a patentee has both “impermissibly broadened the physical or temporal scope of the patent grant” and caused some “anticompetitive effect.”129 Where the patentee’s behavior remains within the grant of the patent right to exclude, however, there can never be patent misuse.130 In response to concerns that this judge-made doctrine was vague, unpredictable, and overbroad, Congress exempted several specific behaviors from the doctrine by adding § 271(d): for example, enforcing a patent or refusing to license cannot constitute patent misuse.131
Equitable estoppel arises when a patentee misleads an alleged infringer into believing that it would not be sued for using the patented technology. The defense may bar all relief on an infringement claim.132 Prosecution laches renders a patent unenforceable where the patentee unreasonably delayed in prosecuting the patent, and the accused infringer or others suffered prejudice by the delay.133