Overview
Patent attorneys routinely confront arguments that patent claims are invalid under 35 U.S.C. § 103 for being obvious. Yet far too often, those arguments inadvertently slip into what the law prohibits: hindsight reconstruction. A proper § 103 analysis requires the advocate to remove their attorney hat, replace it with a science or engineering hat, and engage deeply with the underlying technology.
The first step is understanding the invention—its technical contribution, the problem it solves, and how it advances the field. This means setting aside assumptions about claim strength and focusing on the technical concept. Only after grasping the invention should the patent attorney turn to the prior art and approach it as a person of ordinary skill would: not with answers in hand, but with a genuine problem-solving mindset.
Engineers do not begin with the solution. They begin with the problem, consult available literature, explore known approaches, and build understanding step by step. A strong obviousness analysis mirrors that process. Review the art as if tackling a capstone project or thesis—constructing the reasoning progressively, rather than reverse engineering the claims.
For example: “When considering widget systems, the Smith text book identifies problem X and solves it using approach Y. Publication by Jones teaches alternative technique Z for similar circumstances. A person of skill in the art would have combined these teachings because [insert technical engineering rationale]. This combination discloses all the limitations of Claim 1 of the ’123 Patent.”
This type of reasoning, grounded in technical logic, strengthens the § 103 argument.
Beginning with the claims skews the analysis. The difference between using the claims as a map and mapping the prior art to the claims is critical. Counsel with engineering or scientific experience are often better positioned to understand the perspective of the POSA, the technological landscape, and avoid hindsight bias.
Two common signs of hindsight in obviousness arguments are worth highlighting. First, a conclusory motivation to combine based solely on the fact that references are in the same field. The mere fact that two references are in the same field may explain why a person of skill would review them, but it does not supply the reasoned, articulated explanation required to show why their teachings would be combined in the manner proposed.
Second, the number of references used: although there is no technical limit under Federal Circuit precedent, the more references combined, the more likely the analysis is guided by the claims rather than by technical reasoning. The Federal Circuit has echoed this theme across numerous oral arguments, expressing skepticism when challengers rely on four, five, or six references to construct an obviousness theory. Excessive combining of disparate teachings often signals hindsight. Illustrating this point, a compilation of references is located at the end of this post.
Ultimately, litigation, especially before a jury, is all about the story. Obviousness turns on technical storytelling — and nothing undermines that story faster than hindsight. The most persuasive § 103 arguments stay rooted in the inventor’s world: the state of the field, the problems they faced, the constraints they worked under, and the contribution they actually made. Only with that grounding , and without hindsight distortion, can counsel craft a truly persuasive obviousness analysis under § 103.
The Federal Circuit oral argument blog 717 Madison Place has identified a number of instances highlighting the issues of having too many references and we have compiled the following quotes:
CPI Card Group-Minnesota, INC. v. Multi Packaging Solutions, Inc., 2019-1616, Oral Argument at 15:51–16:14 (Fed. Cir. Mar. 16, 2020) (Judge Newman) (“You know what’s striking? When you get to the point where you have to combine six references in order to make a case for obviousness.”).
In Re Anova Hearing Labs, Inc., 2019-1507, Oral Argument at 24:28–25:24 (Fed. Cir. Feb. 3, 2020) (Judge Moore) (“And, what I’m worried about is a five-reference rejection is the hindsight bias concern of just picking and choosing elements from lots of different random prior art and saying they work together.”).
In Re Neill, 2015-1431, Oral Argument at 22:18–23:50 (Fed. Cir. March 7, 2016) (Judge Moore) (“How often have you seen a four reference obviousness rejection; because, I never have. Not out of the PTO. Never. I’ve seen people try to argue it in litigation, sure. But, I’ve never seen the PTO go to four separate references and cherry pick items and then combine them together.”)
Prime Datum, Inc. v. Baldor Electric Company, 2016-1051, Oral Argument at 16:52–17:22 (Fed. Cir. Nov. 1, 2016) (Judge O’Malley) (“I mean, this is, you have to concede, this is a bit of an odd obviousness finding because we rarely see obviousness determination that requires reference to so many prior art references. I mean, this is, so you have to combine a whole bunch of disparate pieces and parts. And so when you talk about motivation to combine that many things, you get further and further away from a typical obviousness analysis.”)
Intellectual Ventures II LLC v. Ericsson INC., 2016-1803, Oral Argument at 23:56–24:55 (Fed. Cir. Mar. 8, 2017) (Judge Reyna) (“The concern I have here is one of hindsight, and going back and finding obviousness, not from the point of view of a POSITA at the time of the invention, but now, as we understand the invention. It seems to me you have a lot of separate pieces that are being brought together in the various references, and I'm not completely satisfied that the board has given us an adequate explanation as to why all the pieces together work, or why would you put all these pieces together?”).
In re Medicis Pharmaceutical Corp., 2009-1291, Oral Argument at 14:32–16:33 (Fed. Cir. Dec. 14, 2009) (Judge Rader) (“You've got to put together an awful lot of different references in order to get where you want to go. Doesn't that tend to suggest that when you're combining that much, you've got something inventive going on? … Usually, when you have obviousness, you've combined two things in a rather routine way. When you start combining three, that suggests one of skill in the arts got to have an awful lot of understanding.”)
