Sargent v. Hall Safe and Lock Company was a United States Supreme Court case that addressed the issue of whether a patentee could recover damages for infringement of a patent that had been declared invalid. The plaintiff, Sargent, had obtained a patent for a lock and key combination and had sued the defendant, Hall Safe and Lock Company, for infringement. The defendant argued that the patent was invalid and therefore the plaintiff could not recover damages. The Supreme Court held that the patentee could recover damages for infringement of a patent that had been declared invalid. The Court reasoned that the patentee had a right to the exclusive use of the invention and that the defendant had infringed upon that right. The Court also noted that the patentee had invested time and money in the invention and that the defendant had profited from the infringement. Therefore, the Court concluded that the patentee was entitled to damages. The Court also held that the patentee was not required to prove that the patent was valid in order to recover damages. The Court reasoned that the patentee had a right to the exclusive use of the invention and that the defendant had infringed upon that right. The Court also noted that the patentee had invested time and money in the invention and that the defendant had profited from the infringement. Therefore, the Court concluded that the patentee was entitled to damages regardless of the validity of the patent.

Justice Field delivered the dissenting opinion in Sargent v. Hall Safe and Lock Company, arguing that the majority's decision was wrongfully based on a misapplication of state law. He argued that under California law, which governed this case, an employer is not liable for injuries sustained by an employee due to their own negligence or carelessness unless it can be proven that they had knowledge of any dangerous conditions present at the workplace. In this case, there was no evidence presented to suggest that Hall Safe and Lock Company knew about any unsafe working conditions prior to Sargent's injury; therefore, Justice Field believed they should not have been held liable for his damages. Furthermore, he noted that even if such proof existed regarding their knowledge of hazardous conditions at work before Sargent’s accident occurred - which it did not - then liability would still only apply if those hazards were caused by some act or omission on behalf of Hall Safe and Lock Company itself rather than from something outside its control like a third-party contractor as in this instance. As such, Justice Field concluded with his belief that the company should not be found responsible for paying out damages related to Sargent’s injury since none could reasonably be attributed directly back them according to established legal precedent set forth within California state laws governing employers' liabilities towards employees injured while on duty