In the only precedential opinion of this week, Solvay v. Honeywell, the CAFC presented the interpretation of 35 USC 102 (g), providing an opinion that will be useful in teaching patent law. 35 USC 102(g)(2) states that “A person shall be entitled to a patent unless, before such person’s invention thereof, the invention was made in this country by another inventor who had not abandoned, suppressed, or concealed it.” Solvay owns a patent, which has a priority date of October 23, 1995, for methods for making HFC-245fa, one of a group of non-ozone-depleting hydrofluorocarbons, and sued Honeywell for infringing a number of claims of the patent. In 1994, Honeywell contracted with Russian chemists to develop a process for making HFC-245fa and obtained a report documenting the process. In early 1995, Honeywell reproduced the Russian results. In view of the Russian results and having reproduced them in the US, Honeywell obtained summary judgment of invalidity at the District Court, based on 35 USC 102(g)(2). The District Court ruled that Honeywell had made the invention before the priority date of the Solvay patent and that Honeywell was a prior inventor. Additionally, the District Court held that the asserted claims of the Solvay patent where infringed, but not enforceable since the patent was invalid. The CAFC reversed the summary judgment of invalidity, but upheld the summary judgment of infringement. The reversal of the invalidity judgment was based on several facts. The CAFC stated that reproducing the invention is not conception and conception is a required part of inventorship; and, the CAFC also stated that 35 USC 102(g)(2) requires prior inventorship by another in the US. As a result of Honeywell being unable to meet either of these requirements, the CAFC reversed the summary judgment of invalidity. This case underscores the fact that “practicing the prior art is not a defense.” 35 USC 102(a) states that a patent should not be granted if the invention is “known or used by others in this country,” before the invention by the person(s) applying for the patent; however, the courts have ruled that the use for 35 USC 102 (a), has to be public and not concealed. In this case, Honeywell had kept information confidential until after the priority date of the Solvay patent.