The "reverse infringement test" is the accepted test for whether or not a particular claim lacks novelty. In short, if an allegedly anticipating publication would infringe a patent claim, then the invention covered by that claim lacks novelty. However, in Imperial Chemicals Industries Pty Ltd (ICI) v Commissioner of Patents 63 IPR 476 Crennan J held that caution should be exercised in applying such an approach where a prior claim of a broad class of chemicals is compared with a later claim describing a particular chemical compound within that broad class.
This case was an appeal against a decision by a delegate of the Commissioner of Patents that ICI's patent lacked novelty when compared with an earlier patent owned by Lubrizol. The relevant claim of the Lubrizol patent provided for the combination of a refrigerant of hydrocarbons and a lubricant of carboxylic esters. The relevant claim of the ICI patent provided for the combination of a refrigerant of three specific hydrofluorocarbons, 1,1,1,2-tetrafluoroethane, difluoromethane and pentafluoroethane, and a lubricant of carboxylic esters.
The appeal was allowed. ICI's claim was held to be inventive in spite of the fact that the specific ternary composition of hydrofluorocarbons and the lubricant of carboxylic esters was encompassed by the claim of the Lubrizol patent. The Lubrizol patent did not teach or direct the use of ICI"s ternary composition, and was therefore held not to cover such a ternary composition.
Rather than excluding the "reverse infringement test" this case emphasizes that the test should be applied carefully. It is necessary with such chemical patents to consider the material actually disclosed rather than simply investigating the scope of the earlier patent.