When Making Accusations of Infringement, Be Ready to Assert Patent

Earlier this week, in Aspex Eyewear, Inc. v. Clariti Eyewear, Inc., the Federal Circuit held that an allegation of infringement, followed by three years of silence, equitably estopped the patentee from suing the defendant for infringement.

On March 7, 2003, Aspex sent Clariti a letter regarding several of its patents that stated:

It is our understanding that some of the products sold by you may be covered by the claims of the above mentioned patents. In order to minimize further damage, we ask you to immediately confirm for us that you have stopped selling any frames, frame attachments or parts in violation of our rights under the patent[s]. We also ask you to supply us with the identity of the source of these goods and information concerning the number of pieces sold to date. We will then be in a position to reach a prompt and reasonable resolution of this situation.

* * * *

It has been our policy and continues to be our strong intention to fully and vigorously enforce our rights under the exclusive license to these magnetic frame attachments.

* * * *

We look forward to your immediate reply to this very urgent and serious matter.

An identical letter was sent on March 10, 2003, regarding U.S. Patent No. 6,109,747.  Clariti responded on March 18 requesting further information from Aspex on which of its products and which claims of the patents Aspex believed to be in conflict.  Aspex responded with further information on many of the patents on May 12, 2003, but did not include information on the ’747 patent.  Clariti responded on June 26, 2003 that it was not infringing any valid claim of several of the patents listed in the May 12 letter.

No further communication regarding these patents took place until August 23, 2006 when Aspex accused Clariti of infringing the ’747 patent.  After several more letters were exchanged, Clariti brought suit for infringement on March 22, 2007.

The district court granted summary judgment in Clariti’s favor based on the three years of silence after the initial letter regarding the ’747 patent.  The Federal Circuit, in a 2-1 decision, affirmed.

Equitable Estoppel

Normally, a patent owner is entitled to damages for patent infringement dating back six years.  In certain circumstances, however, the patent owner can be estopped from asserting infringement for a shorter time period.  The elements of the defense of equitable estoppel are:

(1) the patentee, through misleading conduct, led the alleged infringer to reasonably believe that the patentee did not intend to enforce its patent against the infringer; (2) the alleged infringer relied on that conduct; and (3) due to its reliance, the alleged infringer would be materially prejudiced if the patentee were permitted to proceed with its charge of infringement.

The Federal Circuit held that several factors contributed to the equitable estoppel holding in this case.  First, its May 12, 2003 letter contained no reference to the ’747 patent.  The defendant testified that by this omission it understood that Aspex had dropped its allegation of infringement with respect to that patent.  Second, Aspex waited three years before further contact with Clariti regarding infringement.  Clariti could reasonably rely on these two factors to assume that Aspex was no longer accusing it of infringement of the ’747 patent.

Judge Rader dissented.  He argued that Aspex’s March 2003 letters did not show that it intended an “immediate and vigorous enforcement of its patent rights.”  Thus, Aspex did not create a clear duty to respond to the accused infringer regarding infringement of the ’747 patent.  He argued that the letter was more like a license negotiation which does not create an estoppel.

He argued that this case is an undue expansion of the defense of equitable estoppel.  The record is devoid of any material prejudice to the defendant that would warrant the outcome in this case.  There is no evidence that Clariti took any action or inaction based on Aspex’s silence.

The lesson from this case is that once you begin sending out letters to potential infringers, especially if they are direct competitors, be ready to continue the discourse or assert the patent.  Silence can be dangerous after the initial contact.

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2 Responses to “When Making Accusations of Infringement, Be Ready to Assert Patent”

  1. Gallo Burch Says:

    Really helpful post. Very sharp commentary and suggested phrasing are most impressive, as are his and your generosity in sharing this explanation and example A life saver , i looked all over for something like this , many thanks!

  2. JOLT Digest » Aspex Eyewear, Inc. v. Clariti Eyewear, Inc. | Harvard Journal of Law & Technology Says:

    [...] and Inventive Step provide an overview of the [...]

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