I own a patent on a text search and retrieval method. The examiner had cited a nebulous concept as prior art, but my attorney was able to discard that, and the patent was issued. I'm now concerned whether that nebulous concept could be used as a defense by an infringer.

2 Answers 2


You can ask your attorney about the ground the prior art was overcome or look up the case in Public PAIR. All of the written back-and-forth between the attorney and the examiner are public record. One key is on what grounds did the reference get defeated. It might have been non-analogous art, not actually contained one or more elements of a claim or been non-enabled (a good bet if it was nebulous). It is also possible that the attorney amended to get around it.

One thing to keep in mind is the phase “it’s good for what it teaches”. A seemingly nebulous reference can still be a teaching, suggestion or motivation to combine references. The references must be enabled but the hint to combine might not be.

It is the case that some newly unearthed prior art might be better at getting your patent invalidated but the courts are not giving much deference to the USPTO these days. A court or PRAB board looks at it with fresh eyes.

Technically, a patent is presumed valid but it is now a very weak presumption so something you got past in examination can still come back in the hands an actual adversary and be convincing to a court. You might have dependent claims that are narrower that survive attack.

  • I think I've seen statistics that show that more than half of patents enforced in infringement actions are successfully defended by a party who established that the patent was invalid..
    – ohwilleke
    May 4, 2022 at 19:16
  • It has been a pendulum between strong and weak patent rights and it has been on the weak side for a couple of decades. Also, I attended a presentation by a patent litigator giving advice to patent prosecutors. He said you get $10k to get a patent granted and I get $100k to show it’s invalid. For a example, prior art can turn up in obscure places in any language published at any point in time before the critical date. May 4, 2022 at 21:33
  • A 1998 study of 300 litigated patents found that 56% were held to be valid and that 46% were found to be invalid in litigation. The was very close to the findings of a 1985 study finding 55% to be valid and a 1994 study finding 56% to be valid which were cited in the 1998 study. papers.ssrn.com/sol3/papers.cfm?abstract_id=118149
    – ohwilleke
    May 4, 2022 at 22:28
  • 1
    Thanks - then it is probably worse since Bilski in 2010 Mayo in 2013 and Alice more recently. May 5, 2022 at 1:16

An infringer can obviously go to court and say “This patent shouldn’t have been issued because of reasons”, and then the court would decide if this is true.

You have the advantage that the patent examiner already knew about this nebulous idea and decided it didn’t matter, but the court can overrule that.

The real question is whether this idea does constitute prior art in the opinion of the court, and that would exactly depend on the idea. Would it be obvious to me, knowing the area of this patent, AND the nebulous idea, to come up with this patent?

But the principle is: If your lawyer convinced the patent examiner that this idea doesn’t matter, then it is more likely that they can convince the court as well. An infringer has likely a better chance to invalidate the patent with things that the patent examiner has never seen.

  • Wouldn't they have to identify some specific reasons for the court to consider?
    – phoog
    May 4, 2022 at 5:42
  • @phoog the court looks at it with fresh eyes and the defense argues a claim is not novel (102) or obvious (103) in light of X, Y and Z. Or, getting more popular, it is drawn to an abstract idea and therefore is not useful (101). May 4, 2022 at 5:56
  • The big difference in court is patent prosecution before an examiner is not (technically) an adversarial process and the examiner is most likely not a trained attorney and does not have the time and money to unearth as much prior art as an adversarial lawyer. May 4, 2022 at 5:59
  • George, in this case the "prior art" was unearthed, but the examiner decided it wasn't actually enough to stop the patent from being granted.
    – gnasher729
    May 4, 2022 at 7:51
  • "the examiner decided it wasn't actually enough to stop the patent". The point GeorgeWhite makes (@George, correct me if I am wrong) is that some legal ramification might go unnoticed to an examiner whose legal background is not strong enough. The adversary's lawyer could prevail in court on the basis of some argument or issue the examiner did not ponder correctly or at all. May 4, 2022 at 9:32

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