Under this analysis, it is incorrect to impose on the patent owner, as the trial court in this case did, the burden of proving that a "public use" was "experimental." These are not two separable issues. It is incorrect to ask: "Was it public use?" and then, "Was it experimental?" Rather, the court is faced with a single issue: Was it public use under § 102(b)?
Thus, the court should have looked at all of the evidence put forth by both parties and should have decided whether the entirety of the evidence led to the conclusion that there had been "public use." This does not mean, of course, that the challenger has the burden of proving that the use is not experimental. Nor does it mean that the patent owner is relieved of explanation. It means that if a prima facie case is made of public use, the patent owner must be able to point to or must come forward with convincing evidence to counter that showing. See Strong v. General Electric Co., 434 F.2d 1042, 1044, 168 USPQ 8, 9 (5th Cir.1970). The length of the test period is merely a piece of evidence to add 972*972 to the evidentiary scale. The same is true with respect to whether payment is made for the device, whether a user agreed to use secretly, whether records were kept of progress, whether persons other than the inventor conducted the asserted experiments, how many tests were conducted, how long the testing period was in relationship to tests of other similar devices. In other words, a decision on whether there has been a "public use" can only be made upon consideration of the entire surrounding circumstances.
While various objective indicia may be considered in determining whether the use is experimental, the expression by an inventor of his subjective intent to experiment, particularly after institution of litigation, is generally of minimal value. In re Smith, 714 F.2d at 1127, 218 USPQ at 976.