Defenses – Laches/Equitable Estoppel

Laches and equitable estoppel are known as “equitable defenses” in that they are not defenses that arise from a statutory basis. Instead they arise from case law when courts tried to balance the equities between the parties and provide some relief to the accused party, when appropriate.

Defenses – Laches

Laches refers to the neglect or delay in one party bringing suit which caused prejudice to the other party. There is no law setting a time limit on when a patent owner can file a patent infringement lawsuit.  However, there is a presumption that a delay of more than six years is unreasonable.  Thus, a defendant can claim that the patent infringement lawsuit is inappropriate because of failure of the patentee plaintiff to bring the suit in a timely fashion.

In arguing the defense of laches, defendants must:

1. Prove that the plaintiff delayed in filing the patent infringement lawsuit for an unreasonable amount of time after it became aware of the infringement, and,
2. That the unreasonable delay caused material prejudice or injury to the defendants.

Plaintiffs can overcome this defense if they prove that either of these circumstances is untrue. One way to do this is to demonstrate that there was a reasonable excuse for the delay in filing suit, such as other patent litigation, licensing negotiations with the defendants, lack of funds, or a patent ownership dispute.  Additionally, the suit may be allowed to continue, but the plaintiff may be limited to recovering damages for only the most recent six years.

The court ultimately decides if the defense of laches applies in a patent infringement lawsuit.

Defenses – Equitable Estoppel

A defendant may argue that a patentee plaintiff is estopped (i.e., precluded) from bringing the action.  If the patentee led the accused infringer to believe that he did not intend to enforce the patent, and the accused infringer relied on that conduct to his or her detriment, the patentee may be prevented from bringing the suit.  The defendant would have to prove that the patentee acted in a way that led the defendant to rely on the conduct, and that reliance on the conduct resulted in material prejudice to the defendant.