Jeewarat v. Warner Bros. Entertainment (CA2/5 B212323 9/3/09):

The 2nd District Court of Appeal for California has reversed the lower courts grant of summary judgment in favor of the employer, and held that when an employee causes a car accident while driving home from a 3 day business conference, even though on his normal commute route, the employer may be held liable for the injuries sustained while on the “special errand” for the employer where the employer cannot show that the employee was acting on his own interest or so deviated from the scope and course of employment that the chain of causation may be considered broken. Ok, that was a mouthful of a sentence, but I think you get the point.

You can find the opinion here.