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Defenses to Patent Infringement

Thu Sep 30th, 2021 by  Patents

Being sued for patent infringement can be a frightening process. Patent litigation can take a significant toll on a business and result in thousands or even millions of dollars in damages. Even if you did the most diligent patent searching and determined that your product does not infringe anyone else’s patent, you still may have missed something, or perhaps your product infringes only a portion of someone else’s patent. If you are sued for patent infringement, you need to be prepared to defend yourself from the allegations using one or more defenses to patent infringement. An Alabama patent litigation attorney goes over the major ones below. 


One of the most common defenses to patent infringement is non-infringement. Using this defense, you argue that your product or process is not the same as the one covered by the patent being asserted against you or that the patent owner failed to meet its burden of proof in showing that you infringed its patent. You may be able to argue this, for example, by showing that the claims of the patent being asserted against you are sufficiently narrow to not encompass your invention.

Patent Invalidity

A non-infringement defense assumes that the patent being asserted against you is valid, but you did not infringe it. A patent invalidity defense asserts that, regardless of whether you infringed the patent or not, it should not have been granted in the first place because it is invalid. Invalidity defenses can be based on one or more of the requirements for patentability. For example, you may argue that:

  • The asserted patent claims unpatentable subject matter 
  • There is prior art disclosing the invention claimed in the asserted patent
  • The invention described in the patent is obvious 
  • The invention described in the patent was insufficiently disclosed 

If the court finds the asserted patent invalid, it can no longer be used as the basis of a patent infringement action. 

Prior Commercial Use

Under § 102 of the Patent Act, a patent may not issue if the claimed invention “was patented, described in a printed publication, or in public use, on sale, or otherwise available to the public” before the patent application was filed. This opens up the door to a “prior commercial use” defense. Using this defense, an alleged infringer may be able to avoid liability by showing that he or she used the invention claimed in the asserted patent commercially at least one year prior to the date the patent application for the asserted patent was filed. 

Equitable Estoppel

The doctrine of equitable estoppel applies in situations where the patentee, through misleading conduct, led the alleged infringer to believe that the patentee did not intend to assert its patent against the infringer. This could occur, for example, where the patentee knew of the alleged infringer’s activities but chose not to pursue a patent infringement claim. If the patentee then sued the alleged infringer many years later, the alleged infringer may be able to argue that the patentee is estopped from asserting its claim. 

Contact an Alabama Patent Litigation Attorney

If you have been sued for patent infringement, you should speak to an attorney who can help you evaluate the allegations and mount a strong defense. To get started, please contact an Alabama patent litigation attorney at Adams IP by calling 251-289-9787 or by using our online contact form.  We serve clients throughout Alabama including Mobile, Huntsville, and Birmingham