One fundamental tenet of the law of obviousness is that it is improper to engage in hindsight – to use the invention described in the claim of a patent as a roadmap to find the various elements of that claim in the prior art, and to then argue that it was obvious to try to combine them. The jury will be instructed that this is improper through the words of the American Intellectual Property Law Association’s Model Jury Instruction – or something equivalent:

“In deciding obviousness, you must avoid using hindsight; that is, you should not consider what is known today or what was learned from the teachings of the patent. You should not use the patent as a road map for selecting and combining items of prior art. You must put yourself in the place of a person of ordinary skill in the art as of the Cutoff Date.” AIPLA Model Patent Jury Instruction 7.0 (2019)

The Federal Circuit Bar Association’s Model Patent jury instruction says the same thing, although not quite so eloquently:

“Do not use hindsight; consider only what was known at the time of the invention [or the patent’s filing date]. Keep in mind that the existence of each and every element of the claimed invention in the prior art does not necessarily prove obviousness. Most, if not all, inventions rely on building blocks of prior art.” FCBA Model Patent Jury Instruction 4.3c (2020)

This rule of law poses a very real pitfall for a trial lawyer who is engaging an expert witness to attack the claims of the opponent’s patent on the ground that the claimed invention would have been obvious to a person of ordinary skill in the art.  If the first thing you do after (or even before) engaging the expert is to send him or her a copy of the patent in suit, you are laying the groundwork for opposing counsel to call your expert’s entire opinion as to obviousness into question:

“Dr. Expert, isn’t it true that the very first thing you did when you were first engaged by Defendant to work on this case was to review the ‘123 patent?

Yes.

And isn’t it true that when you reviewed the ‘123 patent before you read anything else about this case, your review of the ‘123 patent included reading the Summary of the Invention?

Yes

And isn’t it true that when you reviewed the ‘123 patent before you read anything else about his case, your review of the ‘123 patent included reading the description of the inventions found in claims __, __ and __ of the ‘123 patent?

Yes.

So even before you read any of the prior art you’re relying on for your opinions or anything else about this case, you learned exactly how the inventor of   the ‘123 patent had solved the problem of __________________, right?

Yes.

And isn’t it true that after you read how the inventor of the ‘123 patent had put together the various elements of her claimed invention in a way that solved the problem, you already had that information in your mind when you started to search through the prior art?

Yes, I guess I did.”

And of course, there’s a corresponding practice tip for counsel for the patent owner. You will want to explore the sequence in which the alleged infringer’s expert conducted his investigation thoroughly at the expert’s deposition, so that if he made this mistake, you will have a clear record of it to use in his or her cross-examination at trial.