To understand why a patentability search doesn’t answer the infringement question, consider the following scenario: You invent “A” and ask a patent attorney to investigate the patentability of “A”. The patent attorney diligently compares “A” to what is described in the existing patent databases, to see whether “A” has been described before, in which case “A” is not novel and not eligible for patent protection. Further, the patent attorney looks in the patent databases to see whether things similar to “A” have been described, and whether the bits and pieces of “A” have been described in multiple patents in a way that would be obvious to combine together, to produce “A.”
That entire effort focuses on what the prior art describes, where the term “prior art” includes all pre-dating patents and pre-dating published patent applications. (The prior art actually includes patent and non-patent publications, but this posting focuses on patents as prior art because its focus is on the possibility of infringement.) Critically, the patentability assessment effort does not require the patent attorney to investigate what any prior patent actually claims as its patented invention. The fact that “A” or parts of “A” are described in a patent doesn’t necessarily mean that “A” or something similar to “A” is claimed by that patent. Thus, a patent attorney can perform an effective patentability search without having to sort the fine details of what a given patent’s claims actually cover, or whether those claims are valid.
However, to determine whether making, selling, or offering to sell “A” will infringe the preexisting patent rights of someone else, the patent attorney has to make specific and careful evaluations of what each potentially relevant patent claims. Doing so requires the patent attorney to evaluate the claims in each such patent, construe or otherwise interpret what the claim language covers and doesn’t cover, and come to a considered legal opinion about whether “A” falls within that claim language. Further, if it appears that a preexisting patent’s claims cover “A,” the patent attorney generally has to investigate the validity of those claims.
While there’s a lot more to the story than the brief outline above suggests, the useful understanding to take from this posting is that you should never conclude that you’re allowed to make, sell, or offer to sell your invention just because a patent attorney told you that it’s patentable. Put another way, asking for a patentability search is fundamentally different than asking for an infringement risk evaluation.