In Invalidity Search Each patent has a filing date, which is the date on which the patent application was filed. This date is important because it sets the cut-off date for the invention, from which one can show that a patent should not have been granted at all because it was not a novel invention. In some instances, that cut-off date might be earlier than the filing date. For example, patentees can, and often do, file applications based on earlier-issued patents (usually called continuation or divisional applications). In those cases, the patent owner sometimes gets the benefit of the earlier filing date, a.k.a. earliest priority date.

Determining the search cut-off date is a very important aspect of a patent invalidation search. Sometimes the term “critical date” is used to refer to this search cut-off date; however, in patent law, the phrase critical date has a distinct meaning, and it does not always correlate to the search cut-off date that a patent attorney may request.

The cut-off date is dependent on the national laws in the issuing country from which the subject patent originates, and therefore it is important to give due consideration to national patent laws before deciding a cut-off date. There are a number of legal concerns that dictate what cut-off date should be used for a validity search; however, in all cases, this date must be determined by a qualified attorney. Usually patents/ patent applications which are published outside its own jurisdiction, on or before the priority date of subject patent and patent/ patent application published within the same jurisdiction on or before the filing date of the subject patent are considered relevant for the invalidity search.

Oftentimes, the searcher designates the earliest priority date of the patent/application as the cut-off date for the search. However, sometimes the searcher may need to study references published after the earliest priority date (generally 3 to 5 years) to encompass some references, for example published by the same inventor then trace back on to that to find hidden references (published before the earliest priority date) that can form the basis for a legal argument against validity.  Invalidity Search

Put simply, the search cut-off date should be determined to encompass any prior art that might defeat the subject patent’s validity. Ideally, this cut-off should be agreed upon by the searcher and search recipient.  Invalidity Search