UK: Markman, Warner-Jenkinson And Festo - Implications For The European Practitioner

Last Updated: 24 October 2002
Article by Paul Cole

How US patent claims should be interpreted has been the subject of intense debate, and has been considered by the US Supreme Court three times since 1996. Following the recent decision of the Supreme Court in Festo Corporation v Shoketsu Kinzoku1 the rules have hopefully now become more settled. The decisions in the above three cases should be considered together, and the purpose of this article is to summarise the main points that can be gleaned from them and to consider their implications for European practitioners in their day-to-day work of drafting applications and providing instructions to their colleagues in the USA. Of course, where there is any difficulty, or where a legal opinion is required, there is no substitute for the advice of a US practitioner.

At issue in Markman2 was whether the construction of a patent, including terms of art within the claims was for the court to decide, or whether it should be decided by a jury, the right to a jury trial in any action where the value in dispute exceeds $20 being preserved by US Constitution, seventh amendment. The Court decided that the construction of patents, as of other written documents, should be left to the judge since common law practice at the time of framing of the US Constitution and early cases from England both showed that judges, not juries, construed terms in patent specifications, and because this which a task that a judge, from his training and discipline, was in the better position to perform. Following that decision, pre-trial Markman hearings to construe the patent’s claims following motions by defendants for summary judgment have become a routine feature of infringement trials and now account for a major part of the work of the CAFC3.

The continued existence of the doctrine of equivalents was challenged in both Warner Jenkinson v Hilton Davis4 and in Festo. In both cases it was held not to have been rendered obsolete by the entry into force of 35 USC 103 in 1952. In Festo the Court explained that:

"The language in the patent claims may not capture every nuance of the invention or describe with complete precision the range of its novelty. If patents were always interpreted by their literal terms, their value would be greatly diminished. Unimportant and insubstantial substitutes for certain elements could defeat the patent, and its value to inventors could be destroyed by simple acts of copying. For this reason, the clearest rule of patent interpretation, literalism, may conserve judicial resources but is not necessarily the most efficient rule. The scope of a patent is not limited to its literal terms but instead embraces all equivalents to the claims described. See Winans v. Denmead, 15 How. 330, 347 (1854).

It is true that the doctrine of equivalents renders the scope of patents less certain. It may be difficult to determine what is, or is not, an equivalent to a particular element of an invention. If competitors cannot be certain about a patent’s extent, they may be deterred from engaging in legitimate manufactures outside its limits, or they may invest by mistake in competing products that the patent secures. In addition the uncertainty may lead to wasteful litigation between competitors, suits that a rule of literalism might avoid. These concerns with the doctrine of equivalents, however, are not new. Each time the Court has considered the doctrine, it has acknowledged this uncertainty as the price of ensuring the appropriate incentives for innovation, and it has affirmed the doctrine over dissents that urged a more certain rule."

The Court explained both in Warner-Jenkinson and in Festo that the doctrine of equivalents was settled law, and that:

" … the lengthy history of the doctrine of equivalents strongly supports adherence to our refusal in Graver Tank to find that the Patent Act conflicts with that doctrine. Congress can legislate the doctrine of equivalents out of existence any time it chooses. The various policy arguments now made by both sides are thus best addressed to Congress, not this Court."

However, in Warner-Jenkinson, the court responded to concerns that the doctrine of equivalents had taken on a life of its own, unbounded by the patent claims, which conflicted with the definitional and public notice function of claims. It concluded that the doctrine was applicable to the individual elements in a claim, and not to the claim as a whole, and that a claimed element should not be eliminated in its entirety. The essential inquiry was whether the accused product or process contained elements identical or equivalent to each claimed element of the invention:

"An analysis of the role played by each element in the context of the specific patent claim will thus inform the inquiry as to whether a substitute element matches the function, way, and result of the claimed element, or whether the substitute element plays a role substantially different from the claimed element."

The doctrine of equivalents is applicable equally to claims that were allowed unamended and to claims that were rewritten during prosecution. As the court explained in Festo:

"By amending the application, the inventor is deemed to concede that the patent does not extend as far as the original claim. It does not follow, however, that the amended claim becomes so perfect in its description that no one could devise an equivalent. After amendment, as before, language remains an imperfect fit for invention. The narrowing amendment may demonstrate what the claim is not; but it may still fail to capture precisely what the claim is…The amendment does not show that the inventor suddenly had more foresight in the drafting of claims than an inventor whose application was granted without amendments having been submitted. It shows only that he was familiar with the broader text and with the difference between the two. As a result, there is no more reason for holding the patentee to the literal terms of an amended claim than there is for abolishing the doctrine of equivalents altogether and holding every patentee to the literal terms of the patent."

How, then, could the law establish the most appropriate balance between the competing interests of protection for the patentee and certainty for the public? In Festo, the Court was provided with a range of options advanced by the parties and by various amici:

  • There should be an absolute bar on coverage of equivalents where a restriction had been introduced into a claim during prosecution because such restriction was a disclaimer. This "bright-line" approach which had been adopted by the CAFC in Festo was supported by a number of major US companies including IBM, Eastman Kodak, Ford, Intel, Cypress Semiconductor Corporation and United Technologies Corporation.
  • There should be a flexible bar that denied coverage of otherwise patentable subject matter only where it had been clearly and unmistakably surrendered by the patentee. This approach was supported, amongst others, by the American Intellectual Property Law Association.

  • There should be a foreseeable bar which permitted equivalents to be covered unless the limiting effect of amended language with respect to an accused device would have been foreseeable at the time of the amendment to a reasonable person skilled in the art. The foreseeable bar was said to avoid each ‘parade of horribles’ put forward by respective opponents of the flexible bar and the absolute bar, while simultaneously giving effect to the policy considerations advanced by their respective advocates. Thus a patentee could argue for an extended meaning by showing that the alleged infringement was a later development or that a person of ordinary skill in the art could not reasonably have drafted a patent claim that literally encompassed the alleged equivalent. That approach was advocated by IEEE and by the US Government.

The Supreme Court adopted a foreseeability standard and concluded that the claims could cover equivalents that were unforeseeable or that for some other reason the patentee could not reasonably be expected to have described. Since the patentee has, as explained above, the same level of foresight at the time of drafting the application and at the time of submitting amendments, this standard implicitly applies equally to unamended claim language and to claim language that has been amended during prosecution.

The doctrine of prosecution history estoppel requires the claims of a granted patent to be interpreted in the light of events during prosecution so that subject matter that has been surrendered cannot be recaptured. In Festo the court decided that any narrowing amendment made to satisfy a requirement of the Patent Act could give rise to an estoppel. However, the purpose of the estoppel doctrine was to hold the applicant to the representations made during prosecution and the inferences that might reasonably be drawn from any amendment that had been made. Reading the Warner-Jenkinson and Festo decisions together shows that there is a rebuttable presumption that estoppel applies, subject to the following rules:

  1. The onus is also on the patentee to prove that the amendment could not reasonably be viewed as surrendering a particular equivalent, for example because:
    • the equivalent was unforeseeable at the time of the application or amendment, or
    • the reason for the amendment was irrelevant to the equivalent in question; or
    • there was some other reason why the patentee could not reasonably have been expected to have covered the equivalent in question.

  2. If the patentee is unable to explain the reasons for an amendment that narrows an element, then estoppel bars the application of the doctrine of equivalents and the patentee is presumed to have surrendered all subject matter between the broader and the narrower language.

So what can we in Europe do in response to the decisions culminating in Festo and how should we strengthen or alter our practice? It is suggested that if we follow four simple steps, which should already be part of our routine practice, we should be able to send applications and subsequent instructions for amendment to our US colleagues whilst avoiding our clients ending up with unduly narrow claims. These steps are:

  • At the time of filing to have discussed with our clients the range of foreseeable equivalents to the embodiments or examples that have been provided and to check that the claim language covers those equivalents. This may require providing definitions of the technical terms used in the claims to provide "intrinsic" evidence of the meaning of those terms for use at a possible future Markman hearing, and the inclusion of further embodiments or examples to provide support for the range of equivalents that it is intended to cover. European practitioners used to problem/solution analysis should have little difficulty in arriving at broad claim language, at least in the main independent claims, but the importance of definitions and additional embodiments in providing the required "notice" to the public has received less publicity in Europe than its importance demands.

  • During prosecution check for equivalents lying outside the scope of the claims as proposed to be amended. The US Examiner’s well-meaning suggestion that patentable subject matter could be found e.g. if claim 1 were combined with claims 14 and 23, or that he would allow the claim if limited to the use of anhydrous solvents, though inexpensive to follow may not be wise. It is not just a question of what it costs to obtain a granted patent but also what it could cost to have a patent that is unenforceable. As Festo makes clear, the doctrine of equivalents is not an aid for patentees who cut corners during prosecution and introduce limitations they later regret.

  • Ensure that the client or inventor understands the proposed amendment amendment, and has appreciated what subject matter is being given up and what is not. The need for the attorney to work closely with the client in deciding on claim scope and language is emphasized by the Festo decision.
  • Explain the reasons that have prompted amendment, and the intentions underlying the amendment, emphasizing where appropriate the limited nature of those reasons and intentions. Hopefully that will avoid third parties or a court giving the claim an unintentionally narrower meaning when the claims are read, or mis-read.

The Festo opinion should serve as a reminder that the patent specifications that we prepare and the prosecution files that we generate have to be fit to place before a judge. Those who have been involved in litigation will appreciate just how high a standard that implies, and what severe criticism and/or fatal consequences can follow from failing to meet that standard. Festo demonstrates that courts may be prepared to help patentees in unforeseeable difficulty, but that they will have little sympathy for patentees who come with ill-prepared specifications and claims with limitations that it could have been foreseen were unnecessary. Notwithstanding the express inclusion of equivalents in the proposed amended Protocol to Article 69 EPC, the foreseeable standard adopted by the Supreme Court is bound to have influence, explicitly or tacitly, in Europe and elsewhere. Those who criticise the costs of patent drafting and prosecution (usually in the name of the small inventor) should reflect on the effort and skill needed to marshal all the relevant facts, explain them in a coherent manner and provide a clear definition of the rights to be protected. They would then appreciate that legally effective patents, like other legal documents cannot come cheap.

1 Opinion handed down 28 May 2002

2 Opinion handed down 23 April 1996

3 See, for example the CAFC decisions in Schering Corporation and Biogen v Amgen Inc decided 1 August 2000 (defendants succeeded), Phillips Petroleum v Huntsman Polymers decided 22 September 1998 (meaning of "block copolymer"; defendants succeeded) and Pitney Bowes v Hewlett Packard decided 23 June 1999 (plaintiffs’ appeal allowed) are examples amongst very many such decisions.

4 Opinion handed down 3rd March 1997

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

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

In association with
Related Video
Up-coming Events Search
Font Size:
Mondaq on Twitter
Register for Access and our Free Biweekly Alert for
This service is completely free. Access 250,000 archived articles from 100+ countries and get a personalised email twice a week covering developments (and yes, our lawyers like to think you’ve read our Disclaimer).
Email Address
Company Name
Confirm Password
Mondaq Topics -- Select your Interests
 Law Performance
 Law Practice
 Media & IT
 Real Estate
 Wealth Mgt
Asia Pacific
European Union
Latin America
Middle East
United States
Worldwide Updates
Check to state you have read and
agree to our Terms and Conditions

Terms & Conditions and Privacy Statement (the Website) is owned and managed by Mondaq Ltd and as a user you are granted a non-exclusive, revocable license to access the Website under its terms and conditions of use. Your use of the Website constitutes your agreement to the following terms and conditions of use. Mondaq Ltd may terminate your use of the Website if you are in breach of these terms and conditions or if Mondaq Ltd decides to terminate your license of use for whatever reason.

Use of

You may use the Website but are required to register as a user if you wish to read the full text of the content and articles available (the Content). 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 & conditions or with the prior written consent of Mondaq Ltd. You may not use electronic or other means to extract details or information about’s content, users or contributors in order to offer them any services or products which compete directly or indirectly with Mondaq Ltd’s services and products.


Mondaq Ltd and/or its respective suppliers make no representations about the suitability of the information contained in the documents and related graphics published on this server for any purpose. All such documents and related graphics are provided "as is" without warranty of any kind. Mondaq Ltd and/or its respective suppliers hereby disclaim all warranties and conditions with regard to this information, including all implied warranties and conditions of merchantability, fitness for a particular purpose, title and non-infringement. In no event shall Mondaq Ltd 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 or performance of information available from this server.

The documents and related graphics published on this server could include technical inaccuracies or typographical errors. Changes are periodically added to the information herein. Mondaq Ltd and/or its respective suppliers may make improvements and/or changes in the product(s) and/or the program(s) described herein at any time.


Mondaq Ltd requires you to register and provide information that personally identifies you, including what sort of information you are interested in, for three primary purposes:

  • To allow you to personalize the Mondaq websites you are visiting.
  • To enable features such as password reminder, newsletter alerts, email a colleague, and linking from Mondaq (and its affiliate sites) to your website.
  • To produce demographic feedback for our information providers who provide information free for your use.

Mondaq (and its affiliate sites) do not sell or provide your details to third parties other than information providers. The reason we provide our information providers with this information is so that they can measure the response their articles are receiving and provide you with information about their products and services.

If you do not want us to provide your name and email address you may opt out by clicking here .

If you do not wish to receive any future announcements of products and services offered by Mondaq by clicking here .

Information Collection and Use

We require site users to register with Mondaq (and its affiliate sites) to view the free information on the site. We also collect information from our users at several different points on the websites: this is so that we can customise the sites according to individual usage, provide 'session-aware' functionality, and ensure that content is acquired and developed appropriately. This gives us an overall picture of our user profiles, which in turn shows to our Editorial Contributors the type of person they are reaching by posting articles on Mondaq (and its affiliate sites) – meaning more free content for registered users.

We are only able to provide the material on the Mondaq (and its affiliate sites) site free to site visitors because we can pass on information about the pages that users are viewing and the personal information users provide to us (e.g. email addresses) to reputable contributing firms such as law firms who author those pages. We do not sell or rent information to anyone else other than the authors of those pages, who may change from time to time. Should you wish us not to disclose your details to any of these parties, please tick the box above or tick the box marked "Opt out of Registration Information Disclosure" on the Your Profile page. We and our author organisations may only contact you via email or other means if you allow us to do so. Users can opt out of contact when they register on the site, or send an email to with “no disclosure” in the subject heading

Mondaq News Alerts

In order to receive Mondaq News Alerts, users have to complete a separate registration form. This is a personalised service where users choose regions and topics of interest and we send it only to those users who have requested it. Users can stop receiving these Alerts by going to the Mondaq News Alerts page and deselecting all interest areas. In the same way users can amend their personal preferences to add or remove subject areas.


A cookie is a small text file written to a user’s hard drive that contains an identifying user number. The cookies do not contain any personal information about users. We use the cookie so users do not have to log in every time they use the service and the cookie will automatically expire if you do not visit the Mondaq website (or its affiliate sites) for 12 months. We also use the cookie to personalise a user's experience of the site (for example to show information specific to a user's region). As the Mondaq sites are fully personalised and cookies are essential to its core technology the site will function unpredictably with browsers that do not support cookies - or where cookies are disabled (in these circumstances we advise you to attempt to locate the information you require elsewhere on the web). However if you are concerned about the presence of a Mondaq cookie on your machine you can also choose to expire the cookie immediately (remove it) by selecting the 'Log Off' menu option as the last thing you do when you use the site.

Some of our business partners may use cookies on our site (for example, advertisers). However, we have no access to or control over these cookies and we are not aware of any at present that do so.

Log Files

We use IP addresses to analyse trends, administer the site, track movement, and gather broad demographic information for aggregate use. IP addresses are not linked to personally identifiable information.


This web site contains links to other sites. Please be aware that Mondaq (or its affiliate sites) are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of these third party sites. This privacy statement applies solely to information collected by this Web site.

Surveys & Contests

From time-to-time our site requests information from users via surveys or contests. Participation in these surveys or contests is completely voluntary and the user therefore has a choice whether or not to disclose any information requested. Information requested may include contact information (such as name and delivery address), and demographic information (such as postcode, age level). Contact information will be used to notify the winners and award prizes. Survey information will be used for purposes of monitoring or improving the functionality of the site.


If a user elects to use our referral service for informing a friend about our site, we ask them for the friend’s name and email address. Mondaq stores this information and may contact the friend to invite them to register with Mondaq, but they will not be contacted more than once. The friend may contact Mondaq to request the removal of this information from our database.


This website takes every reasonable precaution to protect our users’ information. When users submit sensitive information via the website, your information is protected using firewalls and other security technology. If you have any questions about the security at our website, you can send an email to

Correcting/Updating Personal Information

If a user’s personally identifiable information changes (such as postcode), or if a user no longer desires our service, we will endeavour to provide a way to correct, update or remove that user’s personal data provided to us. This can usually be done at the “Your Profile” page or by sending an email to

Notification of Changes

If we decide to change our Terms & Conditions or Privacy Policy, we will post those changes on our site so our users are always aware of what information we collect, how we use it, and under what circumstances, if any, we disclose it. If at any point we decide to use personally identifiable information in a manner different from that stated at the time it was collected, we will notify users by way of an email. Users will have a choice as to whether or not we use their information in this different manner. We will use information in accordance with the privacy policy under which the information was collected.

How to contact Mondaq

You can contact us with comments or queries at

If for some reason you believe Mondaq Ltd. has not adhered to these principles, please notify us by e-mail at and we will use commercially reasonable efforts to determine and correct the problem promptly.