The group released the audio recording of the full, 68-minute-long statement, which was the first time the Army private's voice has been heard by the public since his arrest nearly three years ago, late Monday, the Huffington Post reported Tuesday.
Manning has admitted to leaking hundreds of thousands of classified documents to WikiLeaks, as well as two videos of American airstrikes, to provoke a debate on U.S. foreign policy. He has pleaded guilty to 10 charges, but not guilty to 12 others, including aiding the enemy and violating the Espionage Act.
"I wanted to figure out the truth," Manning said in the statement to the military court in Fort Meade, Md., and referred to the "delightful blood lust the aerial weapons team seemed to have" as he described a 2007 airstrike in Iraq in which a helicopter fired on a reporter and a driver.
He added the video, released in 2010 by WikiLeaks, "burdens me emotionally."
"Extreme secrecy in our courts, just like in our government's policies and our politics, is an anathema to democracy," the Freedom of Press Foundation said in a statement. "This type of closed-door legal process impairs the public's right to know and journalists' ability to report on matters of public concern."