It could be the biggest trial in modern American history — and most New Yorkers won’t even see it.

Admitted 9/11 mastermind Khalid Sheik Mohammed and four al Qaeda co-conspirators will take the stand in a camera-free New York court when they testify about their roles in the destruction of the Twin Towers.

Mohammed and his cohorts won’t have to face live cameras because of a law that bans broadcasting within a federal court, even for groundbreaking trials that promise to make legal history.

Unless Congress approves legislation granting judges jurisdiction over cameras, the trial will at most appear on closed-circuit TVs that can only be viewed from the courthouse.