A patent is invalid if it is shown to be “obvious” in view of a combination of prior art references (35 USC §103). Patentees, of course, will argue that the proposed combination of references is the product of “impermissible hindsight.” In support of such arguments, the patentees will point to “secondary indicia of patentability.”
Fine, so what exactly are these “secondary indicia?” One indicia is “commercial success.” If the patentee can establish that the patented product was a commercial success AND that the success was the result of the patented features, i.e. establish a “nexus” between the patent and the success, this suggests that the invention was unobvious. Often attempted, rarely achieved – until now. (Hearing Components, Inc. v. Shure Inc.)
At trial, Hearing Components established that a licensing fee for a covered product was more than cut in half when the patent expired. The court accepted this as supporting the contention that the success of the device was related to the patent. Patent validity upheld.
THE LESSON TO BE LEARNED: If you’re lucky enough to have such favorable facts, use them; but notice how unusual they are!