The Keystone Driller Co. v. General Excavator Co., 1933, was a U.S Supreme Court case that revolved around the issue of patent infringement and unclean hands doctrine in equity law. The Keystone Driller Company had purchased five patents related to earth excavating machines and sued the General Excavator Company for infringing upon these patents. However, it was revealed during the trial that one of those patents (the Hazelton patent) had been procured through fraudulent means by bribing a witness to withhold evidence about prior use of similar technology which would have invalidated this patent claim if disclosed earlier. This led to an application of "unclean hands" doctrine where courts refuse relief to those who acted unethically or in bad faith regarding their legal claims or defenses at hand irrespective of whether such misconduct is directly relevant to other claims involved in litigation or not. Consequently, due to its unethical conduct involving one out of five patents, Keystone's entire suit against General Excavator was dismissed.

In the dissenting opinion for Keystone Driller Co. v. General Excavator Co., Justice Cardozo argued that the majority's decision to dismiss a patent infringement lawsuit due to unclean hands was too harsh and not in line with precedent or principle. He pointed out that while it is true that fraud had been committed by suppressing evidence, this did not directly relate to the validity of the patents themselves, which were never obtained through fraudulent means. The suppression of evidence occurred during an earlier unrelated case and should have been dealt with separately rather than being used as grounds for dismissal in this case. In his view, dismissing a potentially valid claim because of misconduct in another matter goes beyond what is necessary or justified under the doctrine of unclean hands.