United States: The Supreme Court Reaffirms The Clear-And-Convincing Standard For Patent Invalidity

In Microsoft v. i4i (S. Ct., June 9, 2011), the Supreme Court unanimously affirmed that clear and convincing evidence is needed to prove the invalidity of a U.S. patent. The Court rejected Microsoft's requests to apply the lower preponderance-of-evidence standard, either in general or at least when a fact finder considers evidence not before the U.S. Patent and Trademark Office (PTO).

Background and Jury Instructions in the Lower Court Proceedings

Plaintiff i4i is the owner of a patent for an improved method for editing computer documents. In 2007, it sued Microsoft for infringement based on the operation of certain Microsoft Word products. Microsoft contended i4i's patent was invalid in light of i4i's sale of "S4" software before i4i filed its patent application. Although there was no dispute on when the sale took place, the parties disagreed as to whether the S4 software embodied the claimed invention.

Because the S4 technology was not before the PTO during prosecution of i4i's patent, Microsoft advocated the following jury instruction on burden of proof:

Microsoft's burden of proving invalidity and unenforceability is by clear and convincing evidence. However, Microsoft's burden of proof with regard to its defense of invalidity based on prior art that the examiner did not review during the prosecution of the patent-in-suit is by preponderance of the evidence.

The trial court rejected Microsoft's proposed instruction in favor of an instruction that required clear and convincing evidence to show invalidity based on all prior art, irrespective of whether it was before the PTO. The jury rejected Microsoft's invalidity defense and awarded i4i more than $200 million in damages. The Federal Circuit concluded the trial court's jury instruction was not erroneous.

The Supreme Court Affirms the Clear-and-Convincing Evidentiary Standard

In an opinion by Justice Sotomayor, the Court reviewed 35 U.S.C. 282, which in relevant part provides: (1) "A patent shall be presumed valid"; and (2) "The burden of establishing invalidity of a patent or any claim thereof shall rest on the party asserting such invalidity." Congress did not articulate the force of the presumption in the statute. The Court concluded, however, that the term presumed valid is a common-law term that had a settled meaning when § 282 was enacted. It noted that Radio Corp. of America v. Radio Engineering Laboratories, Inc., 293 U.S. 1 (1934) ("RCA") had held that, for patents, "there is a presumption of validity, a presumption not to be overthrown except by clear and cogent evidence." As a result, the i4i Court decided that presumed valid, as used in § 282, meant that a defendant raising an invalidity defense bore "a 'heavy burden of persuasion,' requiring proof of the defense by clear and convincing evidence."

According to the Court, "RCA leaves no doubt that attached to the common-law presumption of patent validity was an expression as to its 'force,' that is, the standard of proof required to overcome it." The Court presumed Congress meant to incorporate the heightened standard of proof found in the common law and, rejecting a variety of policy arguments raised by Microsoft and some amici, concluded that any "recalibration" of the standard of proof must be made by Congress.

The Standard Is Constant, but Not All Evidence Is Equal

Much of the uncertainty leading up to the i4i decision derived from language in the Supreme Court's recent decision in KSR International Co. v. Teleflex Inc., 550 U.S. 398 (2007) ("KSR"). KSR stated that, when evidence before the fact finder was not before the PTO during procurement, "the rationale underlying the presumption-that the PTO, in its expertise, has approved the claim-seems much diminished." In i4i, the Supreme Court harmonized KSR with its conclusion that the statute requires a clear-and-convincing standard of proof of invalidity. New evidence supporting an invalidity defense may "carry more weight" before the fact finder than evidence previously considered by the PTO. As articulated by Judge Rich in American Hoist & Derrick Co. v. Sowa & Sons, Inc., 725 F.2d 1350 (Fed. Cir. 1984):

When new evidence touching validity of the patent not considered by the PTO is relied on, the tribunal considering it is not faced with having to disagree with the PTO or with deferring to its judgment or with taking its expertise into account. The evidence may, therefore, carry more weight and go further toward sustaining the attacker's unchanging burden.

Thus, the judgment of the PTO "may lose significant force" if the PTO did not have all material facts before it, and the challenger's burden to persuade the jury of invalidity may be easier to sustain. The clear and convincing standard, however, remains "constant and never changes."

Jury Instructions

The Court advised that jury instructions may be formulated for situations where evidence before the fact finder was not before the PTO. For example, "the jury may be instructed to consider that it has heard evidence that the PTO had no opportunity to evaluate before granting the patent." The jury may also be instructed to consider whether evidence presented to it differs from that evaluated by the PTO. In either case, the jury may be instructed to "evaluate whether the evidence before it is materially new, and if so, to consider that fact when determining whether an invalidity defense has been proved by clear and convincing evidence." The Court noted, no doubt to Microsoft's disappointment, that seeking such instructions on appeal is "far too late."

The Concurrences

Justice Thomas wrote a separate concurrence in the judgment of the Court, but he did not accept its reasoning. In finding the statute silent as to the standard of proof, he concluded RCA was therefore controlling.

Justice Breyer's concurrence, which was joined by Justices Scalia and Alito, addressed certain limitations of the majority decision. Although these concurring Justices joined the Court's reasoning in full, Justice Breyer emphasized that standards of proof and persuasion apply only to questions of fact, not to questions of law. Questions of fact include when a product was first sold or whether a prior art reference was published. On the other hand, questions of law include whether the given facts show a product was in "public use" or whether an invention was novel and nonobvious. Justice Breyer suggested that courts "can help to keep the application of today's 'clear and convincing' standard within its proper legal bounds by separating factual and legal aspects of an invalidity claim, say, by using instructions based on case-specific circumstances that help the jury make the distinction or by using interrogatories and special verdicts to make clear which specific factual findings underlie the jury's conclusions." He added, "By preventing the 'clear and convincing' standard from roaming outside its fact-related reservation, courts can increase the likelihood that discoveries or inventions will not receive legal protection where none is due."

What This Means to You

With Microsoft v. i4i, the Supreme Court confirmed the status quo, that the clear-and-convincing standard is the single standard for proving patent invalidity. The Court acknowledged, however, that the burden of proof may be easier to meet when evidence touching the validity of the patent was not considered by the PTO. The Court has suggested that the lower courts and litigants consider using both jury instructions and special jury interrogatories. That suggestion may have a material and lasting impact on patent litigation practice. Whether you are seeking to enforce your patent rights or to defend against a charge of infringement, if you have questions about i4i, please give us a call.


The content of this article is intended to provide a general guide to the subject matter. Specialist advice should be sought about your specific circumstances.

To print this article, all you need is to be registered on Mondaq.com.

Click to Login as an existing user or Register so you can print this article.

In association with
Related Topics
Related Articles
Related Video
Up-coming Events Search
Font Size:
Mondaq on Twitter
Mondaq Free Registration
Gain access to Mondaq global archive of over 375,000 articles covering 200 countries with a personalised News Alert and automatic login on this device.
Mondaq News Alert (some suggested topics and region)
Select Topics
Registration (please scroll down to set your data preferences)

Mondaq Ltd requires you to register and provide information that personally identifies you, including your content preferences, for three primary purposes (full details of Mondaq’s use of your personal data can be found in our Privacy and Cookies Notice):

  • To allow you to personalize the Mondaq websites you are visiting to show content ("Content") relevant to your interests.
  • To enable features such as password reminder, news alerts, email a colleague, and linking from Mondaq (and its affiliate sites) to your website.
  • To produce demographic feedback for our content providers ("Contributors") who contribute Content for free for your use.

Mondaq hopes that our registered users will support us in maintaining our free to view business model by consenting to our use of your personal data as described below.

Mondaq has a "free to view" business model. Our services are paid for by Contributors in exchange for Mondaq providing them with access to information about who accesses their content. Once personal data is transferred to our Contributors they become a data controller of this personal data. They use it to measure the response that their articles are receiving, as a form of market research. They may also use it to provide Mondaq users with information about their products and services.

Details of each Contributor to which your personal data will be transferred is clearly stated within the Content that you access. For full details of how this Contributor will use your personal data, you should review the Contributor’s own Privacy Notice.

Please indicate your preference below:

Yes, I am happy to support Mondaq in maintaining its free to view business model by agreeing to allow Mondaq to share my personal data with Contributors whose Content I access
No, I do not want Mondaq to share my personal data with Contributors

Also please let us know whether you are happy to receive communications promoting products and services offered by Mondaq:

Yes, I am happy to received promotional communications from Mondaq
No, please do not send me promotional communications from Mondaq
Terms & Conditions

Mondaq.com (the Website) is owned and managed by Mondaq Ltd (Mondaq). Mondaq grants you a non-exclusive, revocable licence to access the Website and associated services, such as the Mondaq News Alerts (Services), subject to and in consideration of your compliance with the following terms and conditions of use (Terms). Your use of the Website and/or Services constitutes your agreement to the Terms. Mondaq may terminate your use of the Website and Services if you are in breach of these Terms or if Mondaq decides to terminate the licence granted hereunder for any reason whatsoever.

Use of www.mondaq.com

To Use Mondaq.com you must be: eighteen (18) years old or over; legally capable of entering into binding contracts; and not in any way prohibited by the applicable law to enter into these Terms in the jurisdiction which you are currently located.

You may use the Website as an unregistered user, however, you are required to register as a user if you wish to read the full text of the Content or to receive the Services.

You may not modify, publish, transmit, transfer or sell, reproduce, create derivative works from, distribute, perform, link, display, or in any way exploit any of the Content, in whole or in part, except as expressly permitted in these Terms or with the prior written consent of Mondaq. You may not use electronic or other means to extract details or information from the Content. Nor shall you extract information about users or Contributors in order to offer them any services or products.

In your use of the Website and/or Services you shall: comply with all applicable laws, regulations, directives and legislations which apply to your Use of the Website and/or Services in whatever country you are physically located including without limitation any and all consumer law, export control laws and regulations; provide to us true, correct and accurate information and promptly inform us in the event that any information that you have provided to us changes or becomes inaccurate; notify Mondaq immediately of any circumstances where you have reason to believe that any Intellectual Property Rights or any other rights of any third party may have been infringed; co-operate with reasonable security or other checks or requests for information made by Mondaq from time to time; and at all times be fully liable for the breach of any of these Terms by a third party using your login details to access the Website and/or Services

however, you shall not: do anything likely to impair, interfere with or damage or cause harm or distress to any persons, or the network; do anything that will infringe any Intellectual Property Rights or other rights of Mondaq or any third party; or use the Website, Services and/or Content otherwise than in accordance with these Terms; use any trade marks or service marks of Mondaq or the Contributors, or do anything which may be seen to take unfair advantage of the reputation and goodwill of Mondaq or the Contributors, or the Website, Services and/or Content.

Mondaq reserves the right, in its sole discretion, to take any action that it deems necessary and appropriate in the event it considers that there is a breach or threatened breach of the Terms.

Mondaq’s Rights and Obligations

Unless otherwise expressly set out to the contrary, nothing in these Terms shall serve to transfer from Mondaq to you, any Intellectual Property Rights owned by and/or licensed to Mondaq and all rights, title and interest in and to such Intellectual Property Rights will remain exclusively with Mondaq and/or its licensors.

Mondaq shall use its reasonable endeavours to make the Website and Services available to you at all times, but we cannot guarantee an uninterrupted and fault free service.

Mondaq reserves the right to make changes to the services and/or the Website or part thereof, from time to time, and we may add, remove, modify and/or vary any elements of features and functionalities of the Website or the services.

Mondaq also reserves the right from time to time to monitor your Use of the Website and/or services.


The Content is general information only. It is not intended to constitute legal advice or seek to be the complete and comprehensive statement of the law, nor is it intended to address your specific requirements or provide advice on which reliance should be placed. Mondaq and/or its Contributors and other suppliers make no representations about the suitability of the information contained in the Content for any purpose. All Content provided "as is" without warranty of any kind. Mondaq and/or its Contributors and other suppliers hereby exclude and disclaim all representations, warranties or guarantees with regard to the Content, including all implied warranties and conditions of merchantability, fitness for a particular purpose, title and non-infringement. To the maximum extent permitted by law, Mondaq expressly excludes all representations, warranties, obligations, and liabilities arising out of or in connection with all Content. In no event shall Mondaq and/or its respective suppliers be liable for any special, indirect or consequential damages or any damages whatsoever resulting from loss of use, data or profits, whether in an action of contract, negligence or other tortious action, arising out of or in connection with the use of the Content or performance of Mondaq’s Services.


Mondaq may alter or amend these Terms by amending them on the Website. By continuing to Use the Services and/or the Website after such amendment, you will be deemed to have accepted any amendment to these Terms.

These Terms shall be governed by and construed in accordance with the laws of England and Wales and you irrevocably submit to the exclusive jurisdiction of the courts of England and Wales to settle any dispute which may arise out of or in connection with these Terms. If you live outside the United Kingdom, English law shall apply only to the extent that English law shall not deprive you of any legal protection accorded in accordance with the law of the place where you are habitually resident ("Local Law"). In the event English law deprives you of any legal protection which is accorded to you under Local Law, then these terms shall be governed by Local Law and any dispute or claim arising out of or in connection with these Terms shall be subject to the non-exclusive jurisdiction of the courts where you are habitually resident.

You may print and keep a copy of these Terms, which form the entire agreement between you and Mondaq and supersede any other communications or advertising in respect of the Service and/or the Website.

No delay in exercising or non-exercise by you and/or Mondaq of any of its rights under or in connection with these Terms shall operate as a waiver or release of each of your or Mondaq’s right. Rather, any such waiver or release must be specifically granted in writing signed by the party granting it.

If any part of these Terms is held unenforceable, that part shall be enforced to the maximum extent permissible so as to give effect to the intent of the parties, and the Terms shall continue in full force and effect.

Mondaq shall not incur any liability to you on account of any loss or damage resulting from any delay or failure to perform all or any part of these Terms if such delay or failure is caused, in whole or in part, by events, occurrences, or causes beyond the control of Mondaq. Such events, occurrences or causes will include, without limitation, acts of God, strikes, lockouts, server and network failure, riots, acts of war, earthquakes, fire and explosions.

By clicking Register you state you have read and agree to our Terms and Conditions