The United States Court of Appeals for the Third Circuit has held that when a driver of an automobile is injured by a "second collision" with a defectively designed automobile headrest caused by a collision with another car whose driver was negligent, the plaintiff has the burden of showing how the damages should be apportioned between the manufacturer of the headrest and the negligent driver.
Huddell v. Levin, 537 F.2d 726 (3d Cir. 1976).
Products Liability - Second Collision - Enhanced Injuries - Apportionment of Damages,
Duq. L. Rev.
Available at: https://dsc.duq.edu/dlr/vol15/iss4/10