18 days after receiving the loaner car, Heyden got drunk (again) on whiskey, got into the loaner car, and crashed into Plaintiff, Walters. Walters sued Defendant Allways for negligent entrustment. The basic argument being that Allways was negligent in giving Heyden a vehicle to drive when he was obviously drunk. That is, giving a drunk man a car and putting him on the road is negligent (i.e. stupid), and the Defendant is responsible for the damage resulting from Heyden's driving. Defendant should have known that the drunk they were giving a car might crash the car damaging property or causing injury or death. This is similar in reasoning to dram shop and other theories of liability.
Defendant filed a motion for summary judgement against Plaintiff Heyden which the trial court granted. Heyden appealed and won with the appellate court determining there were fact issues regarding proximate cause. Defendant appealed to SCOTUS. To find out what happened at SCOTUS keep reading.