Apple has been found guilty of taking part in a conspiracy to fix the price of e-books.
A federal judge in the United States has ruled that the company plotted with five publishers to push up the price of e-books.
Apple was accused of pursuing the conspiracy to undercut Amazon's e-book dominance, causing some prices to rise to between $US13 - $US15 from the $US10 dollars that Amazon charged.
Manhattan district Judge Denise Cote says Apple was not only a willing participant in the conspiracy, it was the ring leader.
Without Apple's orchestration of this conspiracy, it would not have succeeded as it did in the spring of 2010," she said.
The five publishers previously settled and the decision could expose Apple to substantial damages.
The BBC reports Penguin settled its case for $US75 million. Hachette, HarperCollins and Simon Schuster created a $US69 million fund for refunds and Macmillan settled for $US26 million.
Another hearing is to be held to determine damages to be imposed on Apple.
CNN reports the company is likely to appeal the ruling.