Therasense v. Becton Dickinson: Rethinking the Status of Patents as Technical Documents

Earlier this week the Federal Circuit issued its en banc decision in Therasense v. Becton Dickinson, which essentially made it more difficult to establish inequitable conduct. The decision has been reported and analyzed widely over the Internet, for example on the Patently-O and Patent Docs blogs. This post discusses one aspect of the case I find interesting, which is the problems that can occur when the PTO and courts unjustifiably assume that "legalese" statements appearing in patents constitute technical disclosures. To illustrate, let me begin by summarizing how Therasense (now Abbott Diabetes Care, and referred to in the decision and in this post simply as Abbott) got into trouble in the first place.

Abbott owns US patent number 4,545,382 (the ‘382 patent), which issued in 1985 and is directed towards a sensor comprising an electrode with enzyme bound to its external surface. In the specification, the ‘382 patent includes the following sentence (referred to herein as the "Sentence") which was the root cause of Abbott's alleged inequitable conduct: "Optionally, but preferably when being used on live blood, a protective membrane surrounds both the enzyme and the mediator layers, permeable to water and glucose molecules."

The Sentence refers to a protective membrane, employed to protect the electrode from being "fouled" by components of whole blood, such as red blood cells. As discussed later, it is Abbott's contention that at that time, as a practical matter, one of skill in the art would have considered it necessary to employ such a protective membrane when using the electrode in a whole blood. Nevertheless, as is typical practice in the drafting of patents, whoever drafted the patent (presumably a patent attorney or agent) identified the protective membrane as "optional but preferable" rather than mandatory. This is quite reasonable, in view of all the cases in which patentees have found their rights limited by unnecessarily limiting language appearing in the patent specification. The patent attorney prudently sought to avoid an unnecessarily restrictive interpretation of the scope of the claimed invention, in case it turned out to be possible to practice the invention without a protective membrane. When understood in this context, note that the "optional but preferable" language should not be interpreted as a technical disclosure that use of the electrode in live blood without a protective membrane would have been enabled at the time.

Abbott also prosecuted a counterpart to the ‘382 patent in Europe, containing the same "optionally, but preferably" language. The European Patent Office (EPO) cited as prior art against the application a German reference which required the use of a diffusion-limiting membrane. It is important to recognize that a diffusion-limiting membrane serves a very different purpose than a protective membrane. A diffusion-limiting membrane is used to slow the flow of glucose to the electrode, which was necessary for earlier electrodes that could not deal with a rapid influx of glucose, not to protect the electrode fouling.

In order to distinguish over the German reference, Abbott argued that the membrane mentioned in its patent application is a protective membrane, not a diffusion-limiting membrane. Abbott pointed out that the Sentence specifically notes that the protective membrane must be permeable to glucose molecules, and hence not diffusion-limiting as the membrane in the German reference. The arguments submitted by Abbott to the EPO characterized the protective membrane in their application as optional, parroting the language of the Sentence, but this was really tangential to the argument they were making, which was based on the distinction between protective and diffusion-limiting membranes. Unfortunately for Abbott, the briefs submitted to the EPO in 1994 and 1995 included representations that would come back to haunt them in the US, such as "[i]t is submitted that this disclosure [i.e., the Sentence] is unequivocally clear. The protective membrane is optional . . ..”

A few years later, in 1997, Abbott was prosecuting a different patent application in the US patent office that included claims directed to a sensor that did not require a protective membrane when used in whole blood. The ‘382 patent was cited by the PTO as prior art. To overcome the rejection, Abbott argued that one of skill in the art at the relevant time would have felt that the sensor disclosed in the ‘382 patent required the use of a membrane, notwithstanding the "optionally, but preferably" language appearing in the ‘382 patent specification.

In response to an examiner’s request for evidentiary support, Abbott submitted a declaration by Abbott's Director of Research and Development (Dr. Sanghera) stating that "one skilled in the art would not read [the Sentence] to teach that the use of a protective membrane with a whole blood sample is optionally or merely preferred." In submitting the affidavit, Abbott's patent attorney (Lawrence Pope) represented that "one skilled in the art would not . . . have read the "optionally, but preferably" language . . . as a technical teaching but rather mere patent phraseology." [Emphasis added]

In other words, Abbott argued that the "optionally, but preferably" language did not represent a technical disclosure of the state-of-the-art, but rather was an example of patent legalese inserted by the patent after to avoid unnecessarily limiting the scope of the patented invention. Note that there's nothing wrong with this, it is quite proper under some circumstances for an inventor to obtain patent claims that cover embodiments of her invention that employ after-arising technologies that were not part of the prior art at the time the patent application was filed.

In the declaration and accompanying argument apparently worked, and the application issued as US patent number 5,820,551, (the ‘551 patent), the patent that was ultimately held to be unenforceable for inequitable conduct by the district court based on Abbott's failure to disclose to the PTO the briefs filed to the EPO. The district court was evidently bothered by the appearance that in one forum, to suit its purposes, Abbott asserted that the term “optionally” is mere "patent phraseology" which in fact means "necessarily," while in a different forum it appeared to have argued that the same language is "unequivocally clear," i.e., "optionally" actually means "optionally."

In my view, the representations made to the US and European patent offices are not necessarily inconsistent. The problem is, the district court assumed that the "optional but preferable" language appearing in the patent is a technical disclosure, which it interpreted as a disclosure that one of skill in the art would have been able to use the electrode without a protective membrane. In fact, the language is better understood as patent legalese, or in the words of Abbott's attorney "patent phraseology," not intended as a technical disclosure but as language introduced into the specification to avoid unnecessarily limiting the scope of the patented invention.

The declaration and arguments made to the US PTO essentially made this point, and argued that one of skill in the art would have recognized this as patent legalese rather than a technical disclosure of the state-of-the-art. Before the EPO, Abbott does not appear to have argued that the state-of-the-art would have allowed the use of the electrode without a protective membrane, which is tangential to the argument it did make, which was based on the distinction between protective and diffusion-limiting membranes. Abbott's briefs to the EPO merely parroted the “optionally” language of the specification to make it clear that as a legal matter, Abbott did not intend to disclaim patent protection for electrodes used without a protective membrane, on the eventuality that this might become feasible someday.

In this case, Abbott was faced with a rejection based on patent legalese appearing in one of its own patents. But this sort of thing happens all the time, and often the patent cited as prior art is owned by a third party. In prosecuting patent applications, I have on numerous occasions been frustrated by the patent legalese appearing in patents asserted by examiners as prior art. These patents often include disclosure that is clearly wrong as a technical matter, and evidently was introduced into the patent specification by the patent drafter, but it can be difficult convincing a patent examiner that the disclosure appearing in a patent is inaccurate or not enabled. This is essentially the situation in which Abbott found itself, which required it to submit a declaration to the effect that a facially clear statement that use of a protective membrane is "optional” is inaccurate as a technical matter, and should be dismissed as mere patent phraseology.

Formally, the law treats a patent as a technical document. By statute, the patent specification is supposed to be directed towards a technical audience, i.e., the ubiquitous "person having ordinary skill in the art.” Federal Circuit case law attributes a higher degree of credibility to technical disclosure appearing in US patents than it does to other technical documents, such as peer reviewed journal articles. The Federal Circuit has held that the disclosure appearing in patents is presumptively enabled, apparently based on the rationale that the patent office has examined the patent for compliance with the enablement requirement. Other technical documents, such as articles appearing in technical journals, do not receive the same presumption of enablement.

I am quite skeptical with regard to this presumption favoring the credibility of patents over other technical documents. For one thing, patent examiners are charged with examining the enablement of patent claims, not the specification as a whole, which is a very different thing. The fact that a patent issues in no way implies that a patent examiner has reviewed all of the disclosure in a patent and found it to be technically accurate. As exemplified by the Abbott patent, much of the language appearing in patents is "patent phraseology," introduced by the patent practitioner drafting the patent to achieve certain legal objectives, such as broad scope of protection, or the ability to amend the claims a later date, rather than to provide the most accurate technical disclosure. Some patent attorneys might even disclose hypothetical embodiments simply to create prior art, essentially poisoning the well to prevent others from patenting around their invention. It is quite easy for a patent attorney to come up with hypothetical embodiments and describe them in the specification, and usually little downside to the practice (although it did come back to haunt Abbott in this case). It seems to me that the disclosure appearing in a peer-reviewed journal is much more likely to accurately describe the state-of-the-art than a patent, and that the Federal Circuit's presumption in favor of patents has gotten things backwards.

In fact, I would assert that patent law should recognize the reality that much of the disclosure appearing in patents is not technical in nature, but rather patent legalese introduced into the application by patent practitioners for purposes other than accurately describing the state of technology. In my experience, most scientists and other technical people are well aware of this, and recognize that much of what appears in patents is patent phraseology rather than an accurate and objective disclosure of technology. Patent law would do well if it would acknowledge that patents are often drafted for the primary purpose of furthering the legal and business objectives of the patent owner, not as true technical documents.