In some cases, claims will have already been prepared. Claims help focus the searcher's attention on the features thought to distinguish the invention from the prior art.
When claims have not been prepared, the searcher uses his judgment, focusing on features which might be claimed.
Providing the searcher with any known prior art, results of prior searches, and names of companies and inventors likely to be active in the field of the invention will help him find the best references.
* also called "novelty" or "pre-examination" or "preliminary" or "pre-ex"
Sometimes this type of search is called a "right to use" search; that term implies the searcher will review not only active patents, but also expired patents from which one may infer that the invention is in the public domain.
An infringement search may be done early in a product's development, to identify field-dominating patents. However, infringement is often in the details, so one should update the search on the final version of a product before going to market.
Potentially invalidating references may be used
The searcher may also check the maintenance fee status of the patent, do a title search, and determine whether the patent has been involved in litigation.
A collection search is particularly useful to someone entering a new technical field. The purpose of the patent system is to educate the public, and the existing patents contain a wealth of knowledge from which one can draw. Having a library of the pertinent patents on hand may be very useful during product development, particularly if certain patents are identified as important to patentability or infringement risk.
A title search identifies all recorded transfers involving a patent. The searcher looks for an identifies any irregularities such as breaks in the chain of title which might indicate legal confusion about who the true owner of the property is.