USPTO Proposes Adopting "But For" Standard for Materiality

On Friday, October 28, 2016, the Federal Register (Vol. 81, No. 209) published the USPTO’s proposed change of Rule 56 (codified at 37 CFR § 1.56). With the proposed revision, the USPTO is seeking to “harmonize the materiality standard” for the duty of disclosure before the Office with the materiality standard for establishing inequitable conduct in patent litigation.


In 2011, the Federal Circuit decided Therasense, Inc. v. Becton, Dickinson & Co., 649 F.3d 1276 (Fed. Cir. 2010), therein establishing the standard for determining inequitable conduct before the USPTO.
Therasense set forth a two-part test for establishing inequitable conduct on the part of a patentee:

  • First, was a non-disclosed prior art reference “material” to the patentability of one or more disputed claims?
  • Second is there clear and convincing evidence that the patentee knew of a reference and its materiality to patentability of one or more disputed claims and decided not to disclose the reference to the USPTO?

With respect to the first part of this test, the Therasense court held that, for a patentee’s deceptive non-disclosure to be material to patentability, it must be such that the USPTO would not have allowed a claim if the reference had been disclosed. Thus, Therasense established a straightforward “but-for” test for materiality in questions of inequitable conduct. More simply put, the question became, “Did the patentee conceal a reference that it knew would prevent it from getting a patent?”

Current Rule 56

As Rule 56 reads today, the USPTO applies a different standard for determining whether the duty of disclosure has been breached during prosecution. Subsection (b) provides that:

(b) Under this section, information is material to patentability when it is not cumulative to information already of record or being made of record in the application, and

(1) It establishes, by itself or in combination with other information, a prima facie case of unpatentability of a claim; or,

(2) It refutes, or is inconsistent with, a position the applicant takes in:

(i) Opposing an argument of unpatentability relied on by the Office, or

(ii) Asserting an argument of patentability.

A prima facie case of unpatentability is established when the information compels a conclusion that a claim is unpatentable under the preponderance of evidence, burden-of-proof standard, giving each term in the claim its broadest reasonable construction consistent with the specification, and before any consideration is given to evidence which may be submitted in an attempt to establish a contrary conclusion of patentability.

Proposed Rule 56

As the USPTO proposes to revise Rule 56, subsection (b) will instead recite a formulation of the but-for materiality test set forth in Therasense:

(b) Information is but-for material to patentability if the Office would not allow a claim if the Office were aware of the information, applying the preponderance of the evidence standard and giving the claim its broadest reasonable construction consistent with the specification.

Practical Considerations

If the proposed revision is adopted, the test for determining breach of the duty to disclose during prosecution will mirror the test for inequitable conduct, as applied during patent infringement litigation. By applying the same materiality standard both during prosecution and after a patent has granted, the default tactic of charging the patentee with inequitable conduct in virtually every infringement action may be curbed.

As Rule 56 currently reads, it may be more difficult to establish a breach of the duty to disclose than it would to later establish inequitable conduct. The somewhat more straightforward Therasense test may put the materiality question to bed earlier during prosecution. Thus, patentees may soon be able to breathe a sigh of relief when entering the courtroom, no longer worrying about a baseless charge of inequitable conduct in every case.

Furthermore, adoption of the but-for materiality standard during prosecution may encourage applicants to disclose more relevant and not cumulative prior art. The USPTO believes that this will lead to an overall improvement in patent quality as examiners will more easily identify the most relevant prior art.

The USPTO is accepting comments on this proposed rule revision until December 27, 2016 at


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