In the McBride v. Toledo Terminal Railroad Co., 1956 case, plaintiff John McBride was a railroad worker who suffered injuries while on duty and sued his employer, Toledo Terminal Railroad Company under the Federal Employers' Liability Act (FELA). The Supreme Court had to decide whether or not an instruction given by the trial judge to the jury regarding causation in FELA cases was correct. The instruction stated that if negligence of any kind played even slightest part in producing injury then defendant is liable for damages. This became known as "slightest degree" rule which significantly lowered burden of proof for plaintiffs in FELA cases compared to common law standards where they would have needed to prove that negligence was proximate cause of their injuries. In a 5-4 decision, Supreme Court upheld this interpretation stating that Congress intended such liberal construction when it enacted FELA.

In the dissenting opinion for McBride v. Toledo Terminal Railroad Co., it was argued that the majority's decision to uphold a verdict in favor of an injured railroad worker, despite questionable jury instructions, set a dangerous precedent. The dissenters believed that the trial court had erred by instructing jurors they could find negligence on part of the employer if they determined that any act or omission contributed "in whole or in part" to cause injury. They contended this instruction misinterpreted and broadened federal law beyond its intended scope - instead of requiring proof of causation between employer negligence and employee injury, it allowed for liability based merely on some undefined contribution to harm. This interpretation would unfairly burden employers with excessive responsibility and potential damages even when their actions were only remotely related to an accident. Therefore, according to them, such cases should be retried under proper legal standards rather than upheld due solely to sympathy for injured workers.