Apple CEO Tim Cook is testifying on Friday in a high-stakes trial over whether his company Apple has abused its market power.

In the trial that is unfolding in a courtroom in Oakland, California, Cook will be answering questions in-person from Apple lawyers and from attorneys for Epic Games, the maker of the popular videogame Fortnite, which is accusing Apple of being an illegal monopoly.

This is the first time for Cook to be testifying at a witness trial in a courtroom. He will be answering likely hours of questions under oath about one of Apple's most controversial business practices.

The trial comes at a time when there are growing questions about the ironclad grip Apple has over its sizable chunk of the mobile economy.

 

Cook's testimony is capping a three-week trial that has been focused on a 30% commission Apple charges on most purchases made inside of its App Store. Epic Games says consumers should have more options for processing payments, not be forced into paying "the Apple tax."