Bradley Manning's possible prison sentence could hinge on the damage his leaks caused the U.S. government and his motives for releasing the sensitive material.
The sentencing phase of the soldier's court-martial begins Wednesday at Fort Meade, near Baltimore.
He faces up to 136 years in prison for 20 offenses, including espionage, theft and computer fraud.
He was acquitted of the most serious charge, aiding the enemy.
The judge prohibited both sides from presenting evidence at trial about any actual damage the leaks caused national security.
However, lawyers will be allowed to bring that evidence up in his sentencing hearing.
The judge also restricted evidence about Manning's motives during the trial.
Manning could testify during sentencing, though, about his belief that he wanted to expose wrongdoing by sending classified information to the website WikiLeaks.