The ongoing 9/11 case at Guantánamo Bay has hit a critical point. The question at the center of it all: was a key confession obtained freely, or was it shaped by years of C.I.A. torture?

Ammar al-Baluchi, one of the defendants, was interrogated by the C.I.A. over 1,000 times during his three-plus years in custody. Initially, he endured harsh treatment—being beaten, denied sleep, and held naked in a secret Afghan prison. Even after the physical abuse stopped, he remained isolated and cut off from the outside world.

In 2006, he was moved to Guantánamo Bay, where the F.B.I. took over questioning. During a 2007 session, while fully clothed and shackled, Baluchi admitted to providing financial and logistical support to the 9/11 hijackers.

Now, a military judge must decide whether this confession can stand in court. The big issue? Whether it was truly voluntary or influenced by the trauma of his time in C.I.A. custody. The decision could shape the outcome of Baluchi’s death-penalty trial.

This isn’t the only twist in this long-running case. Three other defendants, including Khalid Shaikh Mohammed, are in limbo over plea deals that could spare them the death penalty. A fourth defendant has been deemed unfit for trial.

The stakes are high, and the world is watching as Guantánamo’s legal saga continues to unfold.