[5] Courts can find that there has been direct infringement, however, merely from circumstantial evidence that there must have been at least one instance where the inducement or contribution resulted in the practice of the patented art.
[4] If there are other valid uses for the product, however, or it is "a staple article or commodity of commerce suitable for substantial noninfringing use," the seller has likely not contributed to a third party's infringement under 35 U.S.C. § 271(c).
The two most common defenses to a claim for patent infringement are non-infringement and invalidity.
Case law provides other defenses, such as the first-sale doctrine, the right to repair, and unenforceability because of inequitable conduct.
§ 284, a patent owner is entitled to "damages adequate to compensate for the infringement, but in no event less than a reasonable royalty.
Willfulness is determined from "the knowledge of the actor at the time of the challenged conduct."
Until the 2006 Supreme Court case of eBay v. MercExchange,[10] plaintiffs routinely sought, and were granted, injunctions prohibiting infringement of their patents.
After 2006, injunctions were much harder to obtain, leaving plaintiffs to pursue remedies only for damages.
According to a 2009 article in the Federal Lawyer,[11] courts have been willing to grant such remedies in appropriate cases.