One of the more revealing aspects of PTAB practice is not just how often obviousness rejections are affirmed, but how frequently doctrinal shortcuts appear in the Board’s reasoning. A recent decision (Appeal 2025-001523, Application 17/091,976) affirming an obviousness rejection based on a combination of a CAD-based power grid modeling system with a convolutional neural network image recognition technique offers a particularly clear example of this problem — and an unusual dissent that underscores just how strained the majority’s logic became.

The applicant argued that the Examiner’s proposed modification would render the primary reference unsuitable for its intended purpose. The primary reference relied on measured structural data — including LiDAR and CAD-based models of actual pole locations — to simulate conductor sag and clearance in an electrical grid. The secondary reference used a convolutional neural network merely to classify whether an image contained a pole. Substituting probabilistic image classification for measured structural grid data, the applicant argued, would fundamentally break how the primary system functioned.

That argument sits squarely within a well-established obviousness principle. The MPEP explains that a proposed modification cannot render the prior art invention being modified unsatisfactory for its intended purpose. MPEP § 2143.01(V). This doctrine is not about whether the prior art expressly discourages a modification. It is about technical coherence. The question is whether the proposed combination still allows the primary reference to perform the function it was designed to perform.

Rather than engage with that functional inquiry in any way, the Board reframed the applicant’s argument entirely. The majority asserted that “the argument that the proposed combination of references would render one of the references unsuitable for its intended purpose, or would change its principle of operation, is a teaching away argument,” and then pivoted directly into narrow Federal Circuit teaching away standards requiring express discouragement or criticism in the references themselves. In other words, the Board did not even rebut the applicant’s reasoning, but instead side-stepped the issue.

That move collapses two distinct doctrines into one — and in doing so, quietly raises the bar far beyond what obviousness law requires.

Teaching away is a specific evidentiary concept focused on what a reference says. As the Federal Circuit explained in In re Gurley, a reference teaches away when a person of ordinary skill, upon reading the reference, would be discouraged from following the path set out in the reference, or would be led in a direction divergent from the path that was taken by the applicant. The MPEP tracks this same formulation and requires express or clear discouragement.

But the “unsatisfactory for its intended purpose” doctrine addresses what a modification does. A combination can be non-obvious because it breaks the technical function of the primary reference even where no reference ever criticizes the modification. Teaching away might be one way to show incompatibility, but there is little support to reason that it is the only way, or that the analysis of these two distinct doctrines is interchangeable.

By treating all functional incompatibility arguments as teaching away arguments, the majority effectively required applicants to produce express discouraging language even when the proposed combination arguably destroys the very system the prior art was built to operate. That is not what the MPEP says, and it is not how obviousness doctrine has historically functioned.

The analytical weakness becomes even more apparent when reading the dissent — itself an unusual feature in PTAB decisions. Dissents are rare at the Board, and when they appear, they typically reflect serious concern about the majority’s reasoning. Here, the dissent noted that the CNN reference merely classified whether an image contained a pole, not the physical location of any pole at all. It further pointed out that the primary reference already possessed actual measured pole locations derived from LiDAR and surveys, making it unclear why a skilled artisan would replace reliable structural grid data with image classification outputs. Most importantly, the dissent highlighted the absence of any real technical rationale for the modification beyond hindsight driven by the claims themselves.

In other words, the dissent performed the functional analysis the majority avoided, and in doing so reached the opposite conclusion. While in some cases a dissent can be dismissed as reasonable minds reaching different conclusion, the case here seems to be more of a situation in which the majority used improper logic and a misapprehension of black letter law. Rather than rigorously evaluating whether a proposed modification preserves the technical operation and purpose of the primary reference, some PTAB judges shortcut the inquiry by relabeling incompatibility as teaching away and disposing of it under an express-discouragement standard that was never meant to govern functional breakdowns.

For practitioners, the implication is significant. If functional inoperability arguments are left framed in general terms, the Board may reflexively recharacterize them as teaching away — and then reject them for lack of explicit discouraging language in the art.

Some potential practical takeaways for patent prosecution professionals:

• When arguing that a modification renders a reference unfit for its intended purpose, consider explicitly anchoring the argument in MPEP § 2143.01(V) and the functional inoperability doctrine, not just general incompatibility language.

• In appeal briefs, consider pre-empting the Board’s tendency to recast these arguments as teaching away by explaining up front that intended-purpose inoperability is a distinct obviousness inquiry that does not require express discouragement in the prior art.

• Clearly articulate the technical function the primary reference is designed to perform and walk through how the proposed modification disrupts or defeats that function step by step. Consider whether an expert declaration may be helpful in supporting such an analysis.