What are the chances that an application for a patent on a particular invention will ultimately be granted? How effective would such a patent be in excluding competition? These are the questions that a patentability study seeks to answer.
The heart of a patentability study is a literature search. Usually the search will focus on patent literature. Searching of this kind is an art form and the quality of result will depend on who you hire and how much time they spend.
If the invention is anticipated, I can usually discover that fact within the first hour of searching. On the other hand, no literature search can guarantee discovery of all the relevant prior art. In view of these realities, I recommend a staged approach to literature searching for cost conscious clients. The initial stage is one hour of searching. If the results are not too discouraging, I may recommend a second stage with up to three hours of searching. Search work overlaps with application drafting. I will bill accordingly if subsequently hired to draft a patent application.
In principal, one can draft a patent application without knowing anything about the scope and content of the prior art. In theory, one can begin with very broad claims that are certain to be rejected on first examination. The thinking is that limitations can added over the course patent prosecution as need to overcome the prior art found by the examiner. There are several downsides to this approach. Written this way, the application is unlikely to anticipate and give thorough treatment to the key issues that will arise during prosecution. Over broad statements about what the applicants consider to be their invention often hurt the applicants when they are later compelled to argue that the invention is actually something narrower. For these reasons, I always want to do a prior art search even if my client has already decided to file an application for a patent.