Patent Infringement: Effective Ways to Respond to Rebuttals from Defendants

Patent infringement is a common occurrence in the IP world, which is followed by an infringement allegation. In such a scenario, a patent owner (plaintiff) claiming infringement shares a document backed by evidence with the accused party (defendant). After receiving the document, the defendant usually reverts with a rebuttal to the infringement allegation. This article discusses various methodologies to respond to the defendant’s rebuttal – irrevocably.

Let us first cover patent infringement and how to prove it.

Patent Infringement and its Types

Patent infringement refers to the use of a patent without seeking permission from the patentee. Mainly, there are two types of patent infringements:

  • Direct infringement: In this type of infringement, the patent is directly infringed by the accused party by use, offer to sale or sale in the form of any product.
  • Indirect infringement: Here, the indirect infringer persuades another party to directly infringe a patent by providing the necessary materials.

How to Prove Patent Infringement

Simply accusing an entity of patent infringement is not enough. The plaintiff must provide the necessary evidence of infringement to the defendant. And the best way of obtaining such a proof is by creating an Evidence of Use (EoU)/claim chart illustrating how a product or process includes identical or substantially equivalent evidence for each claim element of the infringed patent. Essentially, this chart is used by the plaintiff to support the document citing infringement by the defendant.

How to Create a Foolproof Claim Chart for Proving Infringement

Figure: Foolproof Claim Chart to Show Infringement

Important Checkpoints for Preparing Effective Claim Charts

Since a patent infringement allegation relies heavily on a claim chart, the plaintiff must ensure that the chart is foolproof. Here are some checkpoints that must be kept in mind while preparing such a chart:

  • The plaintiff should ensure that the claim chart includes direct evidence for every element of the patented invention or that its substantial equivalent is present in the accused product.
  • The plaintiff should also make sure that the features/evidence present in the accused product align with the patent specification.
  • The file wrapper of the patented invention should be studied thoroughly to understand the novel aspect of the patent and other critical elements. The plaintiff should ensure that the evidence for novelty and other critical elements are aligned with the argument present in the file wrapper.

Rebuttal to the Infringement Allegation

When the patent owner (plaintiff) provides the claim chart as an evidence of infringement to the other party (defendant), the latter shares a rebuttal arguing non-infringement of the patent by its product (accused product). This rebuttal can include any of the below-mentioned counterclaims against the plaintiff’s infringement allegations:

  • The defendant can show that the claimed elements are not being infringed by the accused product. This can be done either by arguing that the claim chart fails to show evidence of certain claim limitations or by stating that the product works differently than that shown in the chart.
  • Besides, the defendant can also attempt to invalidate the plaintiff’s patent by showing a prior-art. This pre-dates the patented invention and dismisses the infringement claim.

How to Present the Right Rebuttal Response

Once the plaintiff claims patent infringement, the defendant provides a rebuttal against the infringement claim. This rebuttal can come in two different forms: a non-infringement argument and an invalidity argument against the subject patent. Below, we have dicussed how the plaintiff can effectively respond to these two rebuttal arguments:

Response to Non-Infringement Argument

  • Be neutral and study the argument/evidence presented by the defendant. Then, read the relevant section of the product and the patent claim to provide an appropriate response supporting the infringement and negating the non-infringement claims.
  • Sometimes, the EoU chart does not include direct evidence for certain claim limitations. The defendant can point this out in the rebuttal. In such a case, the burden of proof can be pushed on the defendant if the product operates in the same way, performs the same function, and achieves the same result.
  • Read the rebuttal argument carefully to understand whether the defendant has correctly interpreted the claim limitation(s) that are in line with the patent specification and the file wrapper. If not, then the plaintiff can negate the defendant’s rebuttal by explaining the correct interpretation and at the same time asserting that the accused product includes evidence for the same interpretation.
  • The defendant can sometimes present arguments related to the product/claim interpretation of certain claim terms or claim elements. In such a case, the plaintiff can use the patent specification, file wrapper, and the infringing product for providing an interpretation that is in line with the motivation of the patent.

Response to Invalidity Argument

  • When the defendant cites invalidity of the patent by providing a prior-art, the plaintiff can study the prior-art document, and identify the elements for which the prior-art fails to provide substantial evidence. Thereafter, the plaintiff can provide a detailed response explaining what the prior-art support states and how it is different from the claimed limitations.
  • The patent’s file wrapper can also be studied to provide strong arguments supporting its validity.
  • Lastly, the response for invalidity argument can also be drafted by citing differences between the subject patent and the prior-art embodiments relative to the motivation of the subject patent.


Despite taking all the necessary measures to safeguard their patents from infringement, companies usually find their patents misused. When they send documents showing evidence of infringement to the infringing companies, they often receive rebuttal documents. In order to assert their infringement allegations, it is imperative to respond to the rebuttals effectively.

If you are a plaintiff and are stuck in a similar situation, getting expert assistance is paramount. Sagacious IP’s End to End Patent/Technology Licensing Support is designed to help both large and small companies in handling numerous tasks including preparation of a response to infringement rebuttal.

  • Sandeep Kumar, Ashna Kakkar (ICT Licensing) and the Editorial Team

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