Michael Rix (plaintiff) was rear-ended by a truck manufactured and sold by General Motors Corp. (GMC) (defendant). A GMC dealer had installed a water tank on the truck after the sale. GMC stipulated that a defective brake tube caused the accident but contended that the defect was the result of alterations to the tube sometime after manufacture. Rix sued in Yellowstone County District Court on a theory of strict liability, arguing that there was a manufacturing defect in the tube and that GMC had defectively designed the vehicle by failing to install a dual-braking system, which was necessary based on the foreseeable use of the truck. GMC asserted that its design was safe and that the accident would have occurred even if the truck had a dual-braking system. The trial court instructed the jury that “one who sells a product in a defective condition unreasonably dangerous to the user or consumer” is strictly liable for the harm caused by the product if (1) the seller is engaged in the business of selling such a product,” and (2) the product reaches the consumer “without substantial change in the condition.” The trial court further instructed the jury that Rix had to prove that GMC manufactured and sold the truck “which at the time General Motors sold it was in a defective condition unreasonably dangerous to the consumer,” and that the truck reached the user without substantial change. The jury found for GMC. Rix appealed to the Supreme Court of Montana. Among other things, Rix claimed that the trial court's jury instructions were inadequate.