Prosecution laches

Under U.S. patent law, prosecution laches refers to an "unreasonable and unexplained delay in prosecution.” “The doctrine of prosecution laches is grounded in the need to strike an appropriate balance between the public’s interest in encouraging invention with the public’s competing interest in ‘the free public enjoyment of the useful invention.’ It is an objective measure of reasonableness, applied to a patent applicant’s explanation for his delay, that determines whether that delay is legitimate.”

“The court must evaluate how a reasonable patent applicant would prosecute his patent under plaintiff's circumstances. The inquiry is not directed at plaintiff’s subjective attitude toward the prosecution.” “The applicant’s pecuniary interest in the patent cannot by itself make an otherwise unexplained delay in prosecution reasonable.”

“[T]he burden of proof on a defendant raising the defense of prosecution laches should be no higher than that required to raise other equitable defenses in patent cases, including traditional laches.”