Patent Invalidated Due to Faulty Priority Claim

January 22, 2014

Andrew (A.J.) Tibbetts

What This Means To You

  • When filing a continuation or divisional application, ensure your “priority claim” to your original application is complete and correct.
  • When defending against a lawsuit, double-check the priority claim to ensure it is proper, as any errors could be useful in invalidating the patent and dismissing the lawsuit.


In Medtronic Corevalve, LLC, v. Edwards Lifesciences Corp., the U.S. Court of Appeals for the Federal Circuit (Federal Circuit) addressed whether a patent could be invalidated due to an error in the priority claim.

Medtronic’s patent included language that was plainly erroneous, but Medtronic argued that the intent of the language was clear in context, and the intent should control. The Federal Circuit disagreed, reasoning the public should not have the burden of interpreting a priority claim’s language, and invalidated the patent.

Case Background

Patent applicants are permitted to file follow-on applications to an original application, which may be treated as if they were filed on the same day as the original application so long as several procedural hurdles are met.

At issue in this case were two such procedural hurdles. First, follow-on applications must include a “priority claim” that specifically identifies the original application and other applications (if any) in the chain between the original and current one. Second, a follow-on application has to be filed at the patent office within the time any application to which it directly claims priority is pending (as opposed to, for example, following issuance as a patent).

Understanding the dispute and the Federal Circuit’s decision in this case requires a clear grasp of the priority claim included in Medtronic’s patent, which had a lengthy chain of priority. Unfortunately for Medtronic, two U.S. applications (for simplicity below, “Application A” and “Application B”) had errors in their priority claims resulting from an improper copy-and-paste from a prior application in the chain (“Application C”). The copied language referred to “this application” and was proper in Application C because it claimed direct priority to an earlier application (“Application D”) and was filed while Application D was pending at the patent office. However, Applications A and B included identical language identifying that “this application” claimed direct priority to Application D, which was incorrect since those applications should have claimed priority to Application C. Additionally, Applications A and B could not have properly claimed direct priority to Application D, as they were not filed while Application D was pending.

The defendant, Edwards Lifesciences, argued that because of this erroneous language in the priority claim language of Applications A and B, Medtronic’s patent should not be treated as having been filed as of the filing date of the earliest original application. The practical effect would be that more prior art would be available for Edwards to invalidate Medtronic’s patent, including some of Medtronic’s own earlier patents.

Medtronic countered that the use of the phrase “this application” in Applications A and B should not be interpreted to mean Applications A and B themselves, but rather should be interpreted to mean Application C (the application in which this language first appeared). Medtronic argued that, in the context of the priority claim and the chain of applications, the intent of the language to refer to Application C was clear and that this should control, rather than the explicit language.

Decision Analysis

The Federal Circuit sided with Edwards on this issue, dismissing Medtronic’s argument that the priority claim should not be interpreted based on its plain meaning. The Court reasoned that requiring the public to interpret the priority claim of a patent in context with other applications in the chain placed an unfair burden on the public. The Court additionally ruled that burdening the public in this way was unnecessary given that patent applicants could easily make correct priority claims in their applications.


Patent applicants have a burden to make a complete, clear, and correct priority claim, and any errors in the priority claim can be held against the applicant. Applicants should take care to review their priority claims at filing and potentially again following allowance when there is still an opportunity to fix any errors.

Defendants in litigation should also review priority claims of the patents asserted against them to determine whether there are any errors that could resolve the case quickly.