Aaron Kuhlman (defendant) was driving a truck and trailer unit fully loaded with gasoline when the trailer unexpectedly came loose from the truck, catapulted off the freeway and landed upside down on a roadway. Minutes later, 17-year-old Carol House drove her vehicle into the trailer, ignited the gasoline, and died in the resulting explosion. House’s representative, Siegler (plaintiff), brought suit for negligence and strict liability against Kuhlman, the truck and trailer owner Pacific Inter-Mountain Express (defendant), and the manufacturer of the truck and trailer. The trial court refused Siegler’s request for a jury instruction on res ipsa loquitur and strict liability and the jury returned a verdict in favor of defendants. Siegler appealed and the intermediate court of appeals affirmed. Siegler appealed to the state supreme court.