Res judicata has broad practical applications. Recently, its use was tested in the 2018 patent lawsuit, Sowinski v. California Air Resources Board, which affirmed res judicata applied not only to cases resolved on the merits the facts and evidence of a case—but also ones adjudicated on procedural grounds.

The first lawsuit occurred in 2015, when Richard Sowinski, inventor of an electronic method for claiming pollution tax credits, sued the California Air Resources Board (CARB) over their alleged use of his patent in one of their programs. The court dismissed the complaint because Sowinski failed to respond to motions before the deadline.