The U.S. Supreme Court case Baltimore and Potomac Railroad Company v. Mackey in 1894 revolved around the issue of whether a railroad company could be held liable for damages caused by its negligence, even if the injured party was also partially at fault (contributory negligence). The plaintiff, Mackey, had been injured while working on a construction project near the defendant's railway line when he was struck by one of their trains. He sued for damages arguing that his injuries were due to the negligent operation of the train by employees of Baltimore and Potomac Railroad Company. However, evidence suggested that Mackey himself may have contributed to his own injury through carelessness or lack of attention. Under common law principles then prevalent in many jurisdictions (including District Columbia where this case arose), contributory negligence would completely bar recovery. The Supreme Court ruled against this principle stating it did not apply under federal law governing accidents involving interstate railroads like Baltimore & Potomac’s operations here; instead comparative negligence applied which allows an injured party who is partly at fault still recover some damages proportionate to other party’s share in causing harm.

In the dissenting opinion for Baltimore and Potomac Railroad Company v. Mackey, Justice Brewer argued that the majority's decision was inconsistent with previous rulings of the court. He contended that it was not fair to hold a company liable for damages caused by an employee who had been negligent in their duties, especially when there were no prior indications of incompetence or recklessness on part of the employee. The justice believed this ruling would place an undue burden on employers to constantly supervise their employees' actions, which he viewed as impractical and unreasonable. Furthermore, he disagreed with the majority's interpretation of "fellow servant rule", stating it should only apply if both servants are engaged in common service at time of injury; otherwise employer liability should be limited. In his view, holding companies responsible for all accidents involving their employees could potentially lead to abuse and excessive litigation.