Based on case law, there seem to be two contradictory tests for valid prior art when considering novelty of an invention. I would paraphrase them as:

(i) If information was made accessible and copyable to (even a limited) public audience with sufficient expertise and without explicit/implicit expectations to not copy/distribute the information (i.e. not trying to 'keep secret'), it is considered valid prior art. (See Rosaire v Bariod 1955, Klopfenstein 2004.)

(ii) On the other hand, if a printed publication was not indexed by subject matter and not reasonably possible for an interested researcher to find, it is not considered prior art. (I don't have a specific case for this, but the precedent of a manuscript filed with and publicly accessible via the federal govt, though not indexed by subject matter was highlighted as an example of non-printed publication in this video.)

The contradiction comes about because if information is disclosed to an arm's length party as in (i), that party may not distribute/index the material, and thus it would not be reasonably possible for an interested researcher to find unless he interviewed every person on the planet. So if an invention was disclosed 'publicly', but was not publicly disseminated or indexed such that it was searchable, would an uninformed third party who independently came up with the invention still have the ability to acquire a patent if it filed first?

If the non-disseminated disclosure is considered 'public', then this video states that it would disallow others from patenting. The video also notes that a more apt description for post-AIA is 'first-to-disclose' for this reason.

  • I suppose you're asking specifically for the US? Might be worth to add that tag in this case, the handling could differ in other locations.
    – user18033
    Commented Aug 15, 2017 at 7:37
  • It would be good to know concerning the US, but also would be interested to know if it differs in 'strict novelty requirement' countries.
    – user132162
    Commented Aug 15, 2017 at 16:01

1 Answer 1


From EPO perspective, your question boils down to "when are private discussions considered public"? In general, the information is regarded as having been made public if even just one single member of the public is in a position to gain access to it and understand it, and if there is no obligation to maintain secrecy. You can find a lot more here: http://www.epo.org/law-practice/legal-texts/html/caselaw/2016/e/clr_i_c_3_3.htm

The idea is that it does not really matter if the single member of the public did actually distribute the information, the focus is rather on the question if there was a secrecy agreement or something. In this sense, the word "private" in your questions, implies some sort of secrecy. However, if the secrecy is not expressely agreed, such a disclosure would at least be debatable with the EPO.

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