The definition of causation for the plaintiff's unseaworthiness claim is different from that for the Jones Act negligence claim.
Unseaworthiness is a cause of injury or damage if it was a substantial factor in bringing about injury or damage.
Comments to the Jury Instruction
A different test for causation applies to an unseaworthiness claim as compared to a Jones Act negligence claim. See Ribitzki v. Canmar Reading & Bates, Ltd. Partnership, 111 F.3d 658, 665 (9th Cir.1997) (causation is established for an unseaworthiness claim by showing the condition was a "substantial factor" in causing the injury). Where both Jones Act negligence and unseaworthiness claims exist, the court should instruct on the causal requirements for each. See Lies v. Farrell Lines, 641 F.2d 765, 769 n.7 (9th Cir.1981).
BS&J NOTE: Although a vessel owner has an absolute duty to provide a seaworthy vessel, there is a slightly stronger causal link needed between the injury and the unseaworthy condition than would be needed under the Jones Act. Under the unseaworthiness doctrine, the unseaworthy condition must be a "substantial contributing factor" in bringing about the injury. Under the Jones Act, negligence is the cause of the accident if it is a contributing factor, no matter how slight, in producing the injury.