One of the most common questions that I receive is “Can I go forward with filing a patent application or am I already infringing on existing patents?” This is sort of a tricky question because the client is really asking for two different things: a patentability analysis and an infringement analysis.
The standard for patentability is very different from the standard for infringement, so you need to conduct two separate analyses to fully answer questions like the one above.
Generally, for an invention to be patentable, it must be: 1) a patentable subject matter; 2) novel (overcome a § 102 rejection); 3) non-obvious (overcome a § 103 rejection); and 4) useful. For patentability analysis, all existing patents (both valid and expired), patent applications, published papers, and known inventions are game. When I do a patentability analysis, I line up every single one of the prior art and compare it to the instant invention side-by-side. Then I jot down all of the differences and see if the differences are patentably distinct or trivial. So basically as long as your invention (or a very similar invention) hasn’t already been patented or has been disclosed to the public for more than one year then you have a shot at a patent.
Infringement analysis is similar but again, the standard is different. Also, infringement analysis is typically done when my client is alleging that someone else is infringing on their patent or vice versa. In order for literal infringement to be found, every element of the claims of the patent in question must be found in the accused product. See Pennwalt Corp. v. Durand-Wayland, Inc., 4 USPQ 2d 1737 (Fed. Cir. 1987). Missing even a single element from the product makes the accused product non-infringing to that claim.
Where literal infringement is not found, infringement may still occur under the doctrine of equivalents. See generally Graver Tank v. Line Air Products, 85 USPQ 328, 330 (1995); Atlas Powder Co. v. E.I. Dupont Nemours, 224 USPQ 409, 416 (Fed. Cir. 1984); Warner-Jenkinson Co. v. Hilton Davis Chem Co., 117 S. Ct. 1040 (1997). A product may infringe under the doctrine of equivalents if it performs substantially the same overall function, in substantially the same way, to produce substantially the same overall result as the claimed invention. Dolly Inc. v. Spalding & Evenflo Companies, Inc., 16 F.3d 394, 397 (Fed. Cir. 1994). Each element of the claim must be compared with the accused device to determine whether the accused device contains each element of the claim or its substantial equivalent.
I guess the best way to look at it is that the patentability analysis looks at inventions in their entirety, whereas the infringement analysis looks at claims of registered patents. Also, here’s another way to look at a relationship between a patentability analysis and an infringement analysis: if you are infringing on a patent, then most likely your invention is not patentable. However, if your invention is not patentable, you may not be infringing on a patent.