From The Field

July 8, 2020

On June 30, the Federal Circuit issued a decision invalidating a patent claim on the ground of indefiniteness.  The decision is Pacific Coast Building Products, Inc. v. CertainTeed Gypsum, Inc., et al., Case No. 2019-1524 (Fed. Cir. June 30, 2020) (non-precedential).

The technology at issue is an improved sound-attenuating drywall structure that allows contractors to break the drywall by hand using the standard drywall scoring method (e.g., using a utility knife to make a relatively shallow cut along a drywall board and then breaking the board by hand along that line).  Traditional soundproofing drywalls have an added paper layer that significantly increases the flexural strength of the wall and renders the typical scoring method ineffective.  The asserted claim, claim 21 of U.S. Patent No. 9,388,568 (the “’568 Patent”), claims the improved drywall structure with an element directed to a characteristic of the structure, namely, “a scored flexural strength of the laminated structure is about 22 pounds per ½ inch thickness of the structure.”

The term “scored flexural strength” is not an industry term but rather a term created by the patent.  The specification of the ’568 Patent does not describe how to measure a scored flexural strength other than by reference to an industry standard, ASTM C 473-06a (“Standard Test Methods for the Physical Testing of Gypsum Panel Products”), and describes Figure 3 as showing flexural strength results for one embodiment of the invention.  The district court found the term “scored flexural strength” to be indefinite on the ground that the patent failed to provide sufficient guidance as to how to measure the strength to derive a single value as claimed by the patent. 

The Federal Circuit, reviewing the district court’s decision de novo, agreed that claim 21 was indefinite.  The standard applied by the Federal Circuit is the standard set forth by the Supreme Court in Nautilus, Inc. v. Biosig Instruments, Inc.:  i.e., a patent claim is indefinite, when “read in light of the specification delineating the patent, and the prosecution history, [the claim] fail[s] to inform, with reasonable certainty, those skilled in the art about the scope of the invention.”  Nautilus, 572 U.S. 898, 901 (2014).  The accused infringer, in this case, CertainTeed, bore the burden of proving indefiniteness by clear and convincing evidence.

The Federal Circuit looked at both the intrinsic and the extrinsic evidence presented to the lower court.  On intrinsic evidence, the court found that the two disclosures in the specification, namely, the ASTM standard and Figure 3, both failed to meet the “reasonable certainty” standard.  First, the ASTM standard is not directed to measuring “scored flexural strength.”  It provides for measuring flexural strength of a board under four different test conditions and calls for calculating and reporting “the average breaking load in pounds-force or newtons” for each test condition.  In other words, the measurement of flexural strength under the ASTM standard includes four values with each value representing an average of multiple measurements for a given test condition.  The court found that the specification’s reference to the ASTM standard failed to inform a skilled artisan how to arrive at a single “scored flexural strength” measurement (i.e., “22 pounds per ½ inch thickness of the structure”).     

Figure 3 reports four measurements for four samples (H1-H4) and takes the average of the four measurements as the reported “flexural strength.”  The specification identifies the specific ASTM method used (“ASTM test method C 473, bending test method B”) for the tests referenced in Figure 3.  However, the Federal Circuit nevertheless found that Figure 3 failed to provide sufficient guidance to a skilled artisan.  The court pointed to various test details that the patent might have included but didn’t, such as the orientations of the board for each test, whether those orientations were different, and “whether each sample is a measurement in different orientations.”

The extrinsic evidence was testimony from both sides’ experts.  However, according to the Federal Circuit, while CertainTeed’s expert’s testimony contained detailed testing and analysis, the patentee’s expert’s testimony failed to show that he conducted any testing on his own.  In particular, the Federal Circuit found that CertainTeed’s expert’s testimony, backed up by detailed testing results, showed an additional major source of imprecision of the patent’s teaching resulting from the lack of clarity about the score depth, which was part of the claimed element of the measurement of “scored flexural strength.”  According to CertainTeed’s expert, there were two methods to convert between board thicknesses that could lead to two different scored flexural strengths such that one board might infringe the claim under one method but not the other.  The patentee’s expert, on the other hand, according to the Federal Circuit, failed to present any credible evidence that a skilled artisan at the time of the invention would know which method to use. 

Claim 21 recites a particular value for “scored flexural strength,” i.e., “about 22 pounds per ½ inch thickness.”  The inventors clearly thought that referring to a specific test method used in the ASTM standard was sufficient to apprise one skilled in the art how to measure flexural strength of a given board.  From the patentee’s perspective, it seems harsh that referring to a specific test method in an industry-adopted standard test protocol would not be sufficient to render a claim term definite.  On the other hand, the score depth does appear to be a significant detail impacting flexural strength.  If a sufficiently narrow range of score depths would not have been known to one skilled in the art in this context, then the omission of score depth from the patent’s testing description might support an indefiniteness holding.  Although aspects of the opinion seem unduly harsh to the patentee, other patentees can at least take comfort that the opinion is not precedential. 

This case highlights the importance of providing sufficient descriptions in the specification when claiming an unconventional characteristic of an invention, including how to determine the existence of that characteristic  If patentees should take a more specific lesson from this case, it is not that relying on standards is necessarily insufficient to render terms definite.  The court’s reasoning on that point is suspect and omits important details that were in the patent.  Rather, the more useful lesson might be that a patentee should take care when its tests supporting claims to a functional characteristic depend on factors that are clearly beyond the scope of a standard on which the patentee is relying.  In this case, “score depth” was both relevant and clearly beyond the relevant ASTM standard’s scope.

Authors: Hui Liu and Michael Mauriel