It turns out that Mom was right when she said: “If you can’t say anything nice about someone, don’t say anything at all.” Criticism of the prior art can limit the scope of your claims. In UltimatePointer, LLC v. Nintendo Co., 816 F.3d 816 [118 USPQ2d 1125, 1130] (Fed. Cir. 2016), the Federal Circuit found that the patentee’s disparagement of indirect pointing devices supported the conclusion that such devices were not encompassed by “pointing device” in the claim. The Federal Circuit said that “the repeated criticism of indirect pointing” clearly pointed to the conclusion that the “handheld device” in the claims is limited to a direct-pointing device.
The lesson is to not disparage any feature of the prior art that might be incorporated into a device that you would want to claim infringes your claims. You are free to disparage problems of the prior art that are eliminated by the claimed invention. If you disparage the prior art, however, and the accused infringer’s product suffers from the same problem you criticized, then the accused product may not be found to infringe your claims. And Mom would say, “it serves you right.”