Early in my career as an expert mechanical engineering witness I was retained by Popeil, Inc. in a patent infringement suit against Sunbeam et al.  The patent covered a steam heated hair curler system and Popeil’s patent contained temperatures measured on the curlers during their use.    I paid several women to operate the Sunbeam unit as directed with thermocouples mounted on the plastic curlers.

My expert report contained plots of these measured temperatures.  The judge in the case found the patent was 1) invalid and 2) not infringed. 

Invalidity was based on “published prior art” - a Japanese-language user instruction sheet connected with marketing of a “steam heated hair curler” on one of the smaller islands of Japan. Non-infringement was based on the temperatures I reported being lower than those contained in the Popeil patent.  I had apparently not conducted my tests in the same manner as the Popeil engineer who supplied the data for the patent.  He must have been careful to open and close the curler box rapidly plus allow time for the curlers to reach a high temperature before taking out the next one.  I had allowed the women to proceed as they liked.

The lesson I learned was that the data supplied by an expert should support the arguments made.  I’m sure a completely valid test agreeing with the patent would have resulted from more careful reading of the patent procedures.