Filmmaker George Lucas is suing a British designer who created the costumes for his Star Wars films.
Andrew Ainsworth designed the storm-trooper helmets and was paid $70 (GBP35) each for 50 helmets made for the 1977 film.
But he says he owns the merchandising rights and is entitled to a multi-million dollar pay off.
In 2004 he sold copies of the outfits for $3,600 (GBP1,800) each - but was stopped by Lucas who claims he owns the copyright.
But Ainsworth has hit back claiming the copyright has expired because the uniforms were industrial design, not art.
The U.S. court case is expected to last 10 days.