In what circumstances will a judge consider invalidity as an additional ground for a finding of non-infringement?

He was wrong. Even without the defendant's counterclaim, to hold non-infringement did not preclude a holding of invalidity as an additional ground for decision in favor of a defendant; the public good will usually be served, in such circumstances, by finding invalidity. And to consider that issue was surely proper here, because of the counterclaim asking a declaratory judgment of invalidity. Altvater v. Freeman, 319 U.S. 359, 363, 63 S.Ct. 1115, 87 L.Ed. 1450.¹