When are employers liable for subsequent aggravations of workplace injuries? McKesson v. Lieberman Explained

The Utah Court of Appeals in McKesson v. Lieberman clarified when employers remain liable for subsequent injuries that aggravate original compensable workplace injuries. This case provides important guidance for practitioners handling workers’ compensation claims involving subsequent aggravations.

Background and Facts

In 1995, Lieberman suffered a compensable workplace injury when struck in the head by a fourteen-pound case, causing two herniated cervical disks. After surgery and rehabilitation, McKesson paid initial workers’ compensation benefits. However, in May 1999, Lieberman hit his head on his truck’s door frame, aggravating his neck injury. McKesson denied liability for this subsequent injury, arguing it broke the causal chain from the original workplace accident.

Key Legal Issues

The central issue was whether the Commission applied the correct legal standard for determining liability for subsequent aggravations of compensable workplace injuries. McKesson argued the Commission should have applied the Allen v. Industrial Commission preexisting condition analysis, requiring proof of unusual or extraordinary exertion.

Court’s Analysis and Holding

The court held that subsequent aggravations of compensable workplace injuries are governed by the “natural result” standard from Intermountain Health Care v. Board of Review, not the more stringent Allen analysis. Under this standard, a claimant need only prove the subsequent injury is a natural result of the compensable primary injury. Importantly, the claimant need not show the original accident was the sole cause of the subsequent injury—proving it was merely a contributing cause suffices.

Practice Implications

This decision reinforces that employers bear ongoing liability for compensable workplace injuries, even when subsequent events aggravate those injuries. Practitioners should focus on establishing medical causation linking the subsequent injury to the original compensable injury rather than attempting to prove sole causation. The Commission’s factual findings receive substantial deference and will be upheld unless they exceed the bounds of reasonableness and rationality.