Introduction to the Doctrine of Prosecution Disclaimer
In the U.S., statements made by a patent applicant during the examination process at the Patent and Trademark Office (which patent lawyers refer to as prosecution), can limit the scope of protection provided by the resulting patent. Therefore, your patent lawyer should take great care in the statements he or she chooses to make to the Examiner regarding your invention.
A patent’s scope is determined by its claims. As a result, applicants generally try to articulate the claims so that they will describe the invention in the broadest possible manner, covering a broad range of similar or potentially competitive products or processes. However, these claims are analyzed by an Examiner at the PTO to ensure that they are new and nonobvious when compared to what others have done in the past (the prior art).
This creates a conflict between the desire to achieve the broadest possible protection and the need to define the invention narrowly enough to distinguish it from the prior art. What generally happens is that the claims start out very broad, and then when they are rejected by the Examiner as already taught by certain prior art references, the Applicant will either narrow the claims by amendment or argue that the Examiner’s interpretation of the claims is incorrect.
While these actions are often necessary to achieve allowance and grant of a patent, they also can each limit the scope of protection afforded by the resulting patent. This limiting of the scope of patent claims based on actions taken during prosecution is known as file-wrapper estoppel.
One type of “file-wrapper estoppel” is the prosecution disclaimer doctrine, which holds that an Applicant’s mere arguments, without any corresponding amendment to the claims, can limit the scope of the claims. The other type is prosecution history estoppel, which deals with claim amendments and will be addressed in a future post.
Prosecution Disclaimer in Practice
Whenever an applicant makes a clear and unambiguous argument that a claim does not cover a certain feature, this argument becomes binding on the applicant and the applicant can no longer argue in court that the claim would cover such a feature. Coverage of that feature is considered “disclaimed” by the Applicant and cannot be recovered. The scope of the resulting patent is narrower than it might be if the applicant had said nothing.
Why would an applicant make such a statement? Examiners are required to give a claim the “Broadest reasonable interpretation in light of the specification.” MPEP § 2111. In my experience, many examiners instead give claims the “broadest possible interpretation”, a rather different standard. So, examiners will often argue that a feature of your claim is taught by a prior art reference, when in fact the feature taught in the prior art reference is very different from the feature of your invention.
To get around that rejection and achieve allowance, it is common to argue that the Examiner has made a mistake- that the prior art reference does not teach the feature of your claim, because the claimed feature does not encompass the feature taught in the prior art.
A Hypothetical Example of Prosecution Disclaimer
Suppose an inventor has created a new form of biofuel using oil from soybeans, a legume. His original claim from the patent application is worded as follows: “A method of producing biofuel by extracting vegetable oil from a legume.” In our hypothetical, the examiner rejects this claim because there are numerous methods for the production of biofuels from peanut oil in the prior art, and the examiner states that peanuts are a legume.
In order to increase the likelihood of patentability, the applicant might argue that by using the word “legume”, he is referring only to edible seeds; peanuts exhibit properties of both seeds and nuts and thus fall outside the claim’s scope.
Here the applicant has asserted a specific interpretation of a claim during prosecution, disclaiming coverage of peanut oil. As a result, the applicant cannot later argue for a broader interpretation that would encompass peanut oil. The applicant is bound by its original argument. Using the above example, the owner of a resulting patent could not later succeed in suing a competitor for infringement of the claim based on production of biofuel derived from peanut oil.
Historical Basis and Case Law Examples of Prosecution Disclaimer
Prosecution disclaimer is a common law (judge-made) doctrine that originates in federal court precedent. A good discussion and example of prosecution disclaimer can be found in the Federal Circuit case Southwall Techs. Inc. v. Cardinal IG Co., 54 F.3d 1570 (Fed.Cir.1995). This case also cites to several other important and educational Federal Circuit cases dealing with prosecution disclaimer. See Id. at 1576.
In Southwall, the Court was explicit in defining the principle: “The prosecution history limits the interpretation of claim terms so as to exclude any interpretation that was disclaimed during prosecution”. Id. The Court used the principal to prevent the patentee from arguing an interpretation of “sputter deposited dielectric” that would allow it to continue with a patent infringement suit, because the argument was inconsistent with its position during prosecution. Id. at 1575-59.
The Court also noted that a given claim term must be interpreted consistently across all claims. Once a term has been given a specific meaning with regard to one claim, the same meaning applies to all claims that include that term. Id. at 1579. So, a disclaimer made to achieve allowance of one claim may affect them all.
This formal doctrine of prosecution disclaimer evolved in the Federal Circuit from earlier precedent stating the general principle that prosecution history, including applicant/attorney arguments, should be used in interpreting the meaning of claim terms.
An early Federal Circuit case using the term “disclaimer” is Standard Oil Co. v. American Cyanamid Co., 774 F. 2d 448 (1985). In Standard Oil, the Court stated that “the prosecution history (or file wrapper) limits the interpretation of claims so as to exclude any interpretation that may have been disclaimed or disavowed during prosecution in order to obtain claim allowance.” Id. at 452.
The Practical Import of Prosecution History
Prosecution disclaimer is an important doctrine in patent law. It ensures that an applicant cannot obtain a patent by arguing that its claimed invention is narrow, and then turn around and enforce that patent against competitors with an argument that it is broader.
When prosecuting an application in the U.S., an applicant must be careful about the arguments it makes. Sometimes it is necessary to clarify what the claims cover or do not cover in order to achieve allowance, but those explanations should be limited to the extent possible. It is not a good idea to say more than you need to overcome the prior art, as doing so needlessly risks limiting the scope of the resulting patent.
It should be noted that the doctrine of prosecution disclaimer does not exist in other jurisdictions, such as Europe. In those jurisdictions, claim language stands on its own without reference to the prosecution history of the application. Therefore, a U.S. attorney may need to be especially careful when preparing a Response using the comments of a European applicant, or the applicant’s European counsel.
{ 3 comments }



