It is often a challenge for non-lawyers—including expert witnesses new to patent litigation—to distinguish between the phrases "patent infringement" and "patent invalidity."  Adding to the potential for confusion, these two very different legal concerns are often at issue in a single trial and thus to be considered and decided by the very same judge or jury.  This article clarifies the distinction between infringement and invalidity.

What is Patent Infringement?

Patent litigation usually enters the American legal system when an individual or company that owns a patent sues another party of infringing that patent in United States District Court.  In the field of intellectual property law, a patent is infringed when the owner's exclusive rights in his invention are violated.

Broadly speaking, you infringe the patent of someone else if you use, manufacture, import, and/or sell the invention without their permission.  Such permission is normally granted with a license in the form of a contract between the parties.  In some countries and jurisdictions unlicensed but non-commercial uses of inventions are not considered ripe for infringement suits.

Importantly, patent rights exist within territorial limits.  So, for example, if you are the owner of a U.S. patent but the violation of your rights takes place outside of the United States you may not legally be able to pursue or stop the infringer.

The pursuit and proof of a patent infringement often, therefore, requires proof at least that the invention was used without a license in a place and at a time where the patent was enforceable.  In this context, expert witness testimony is necessary to explain to the judge and jury how the invention was practiced, such as by showing how software source code produced by the defendant implemented all of the steps of at least one patent claim.

When is a Patent Invalid?

As you can probably imagine, defendants in patent infringement lawsuits are not happy to be accused of wrongdoing by someone they don't believe they've hurt.  From the point of view of the defendant and their legal team, the patent may not describe an invention they believe their products actually infringe.  They may feel wronged by the government agency, such as the United States Patent and Trademark Office, that granted a patent that describes something so obvious to them that they can't understand how anyone could consider it an "invention" worthy of an award of monopoly rights.

The part of the case relating to invalidity is thus a counter suit brought by the defendant against the patent's owner.  The objective of this part of the patent litigation is to get the patent thrown out.  If the counter suit is successful, then even if the defendant's products do practice the invention the plaintiff's infringement proof will fail for lack of an enforceable patent.

Thus (and especially prior to 2011's America Invents Act*) most patent litigation in U.S. District Court is fought on two parallel fronts.  The plaintiff's lawyers try to convince the jury that the defendant's products infringe the patent(s) at issue while the defense tries to convince the jury that those patent(s) are invalid.

A patent can be proven invalid by disproving one or more of the requirements for the awarding of a patent, which include that the invention discloses something that is new and non-obvious and that the how to practice the invention is fully disclosed to the public.

Expert Witnesses for Patent Litigation

In a patent infringement lawsuit, each side's lawyers will present testimony from one or more expert witnesses to support their arguments.  For each patent there will be four arguments requiring supporting expert testimony:

  • the patent is invalid (defense expert)
  • the patent is valid (plaintiff expert)
  • the patent is infringed (plaintiff expert)
  • the patent is not infringed (defense expert)

Sometimes one expert will provide testimony to support both arguments for one side for all patents, but more commonly--and especially when there is more than one patent at issue--the judge and jury will hear from many experts in related technologies.

Invalidity and non-infringement can be considered as two independent defenses.  If the defendant prevails on either point, there will be no damages.  In this high-stakes game, the plaintiff hopes to be paid monies for prior infringement (and perhaps also for a going-forward license) but is at risk of losing the patent altogether. 

* With an aim of reducing costs of patent infringement lawsuits, the AIA created a new venue to argue for the invalidity of a patent.  Many defendants now file a challenge to each asserted patent at the Patent Trial and Appeal Board and ask the judge in U.S. District Court to put the plaintiff's infringement suit on hold until after that is decided.

Barr Group's team of electronics and software expert witnesses provide experienced and unbiased source code reviews, expert reports and testimony for product liability, patent infringement, software copyright, and trade secrets litigation involving computer-based technology and software.  HIRE AN EXPERT