There are several different types of patent searches and opinions that may be created. First, the “search” phase may have different purposes, and second, the “opinion” phase may be directed to different needs.
Patentability Search – For the patentability search and opinion, the purpose is to determine if an invention is disclosed in other references, such as patents or other publications. That is, do other patents or publications teach how to make the invention, either within a single patent or publication, or through a combination of patents and publications that are in the same general technical field (called a “field of art” in the patent vernacular).
The reasons for performing a patentability search are that the United States Patent & Trademark office (USPTO) will reject a patent application for lack of novelty if it is completely taught within a single reference patent or publication, or if they deem the invention to be obvious, through a combination of other patents and/or publications.
Because the claims in a patent or published patent application must be supported by a description in the specification portion of the patent and in the drawings, a patentability search and opinion focuses on the text and drawings to determine whether the subject invention has been taught before. If the entire invention is found disclosed within a single patent, the opinion will reflect that the subject invention lacks novelty as you can read from https://www.hngn.com/articles/227862/20200113/what-can-the-experts-at-inventhelp-do-for-you.htm.
If all the features of the subject invention are not found in a single patent, but can be found in two or more patents or other publications in the same field of art, the opinion will reflect that the subject invention lacks non-obviousness. If a single feature of the invention cannot be found within the references located during the search, the opinion will reflect that the invention should be patentable. While experienced searchers will generally find nearly all of the references that might be applicable towards a particular invention, it is always possible that a reference may be overlooked.
Additionally, an examiner at the USPTO may believe that a reference discloses something different than the view of the person who wrote the opinion. Further, an examiner at the USPTO is at liberty to select any reference, that is, any published material that may exist. Thus the examiner may draw upon publications that are not patents or patent applications.
Additionally, during the patent examination process, patent applications are secret for a period of time (typically 18 months), during which no one outside the USPTO can access them to determine whether they might impact the patentability of a particular invention. Lastly, an examiner may draw upon foreign references. While an exhaustive search of foreign patents, patent applications and other non-patent published material may be made, such would come at a typically prohibitive cost and it is all explained in details on https://millennialmagazine.com/2020/01/13/dont-give-up-on-your-invention-idea-turn-to-inventhelp/.
Accordingly, during the search portion for a patentability opinion for filing of an application for a United States patent, only a search of U.S. patents and patent applications that are published will be made. Further, such patentability search may be limited to a particular time frame, typically since 1976, because U.S. patents prior to 1976 are only stored as image files at the USPTO and may not be keywords searchable.
Patents prior to 1976 are typically searched by the classification number in which the fall along with the title of the invention, which can be searched by keyword. It should be noted that the USPTO me soon require foreign searches to be made as part of a special process to accelerate the examination of a patent application. However, the scope of such foreign search has not yet been defined and may add substantially to the costs of obtaining a search for this purpose.