Patrick Semansky, Associated Press
Army Pfc. Bradley Manning, right, is escorted from a security vehicle to a courthouse in Fort Meade, Md., Thursday, Dec. 22, 2011, for what is expected to be the final day of a military hearing that will determine if he should face court-martial for his alleged role in the WikiLeaks classified leaks case.

FORT MEADE, Maryland — Closing arguments started Thursday in the preliminary hearing for an Army intelligence analyst accused of creating the biggest national security leak in U.S. history.

Once the arguments end in the case of Pfc. Bradley Manning, presiding officer Lt. Col. Paul Almanza will have until Jan. 16 to recommend whether the 19-year-old should stand trial for aiding the enemy and 21 other charges. If convicted, he could face life in prison.

It's been nearly 19 months since Manning was charged with giving to the anti-secrecy website WikiLeaks a trove of classified data, including hundreds of thousands of State Department diplomatic cables and raw battlefield reports from Iraq and Afghanistan. There was also video of a laughing U.S. helicopter crew gunning down 11 men, including a Reuters cameraman and his driver, in a clip WikiLeaks called "Collateral Murder."

The reason Manning allegedly gave for the disclosures, in online chats with a confidant who turned him in: "I want people to see the truth."

His lawyers say Manning was a troubled man who shouldn't have had access to classified material, let alone served in Iraq. They argue that security at his workplace was weak and that the published material did little or no harm to national security.

The prosecution's three main witnesses were, like Manning, computer experts.

Adrian Lamo, a one-time convicted hacker, testified he gave investigators records of his May 2010 online chats with a correspondent using the screen name "bradass87" who bragged about engineering "possibly the largest data spillage in American history" from his Army post in Baghdad.

Two computer forensic examiners said they found evidence on Manning's workplace and personal computers that he had downloaded battlefield reports from the military's supposedly secure network and emailed them to WikiLeaks.

The defense called just two witnesses — a sergeant who witnessed one of Manning's fits of rage and a captain who found it odd that intelligence analysts were allowed to load music and other non-work material into computers linked to the classified data network. Manning allegedly downloaded the diplomatic cables onto a rewritable CD labeled "Lady Gaga," while lip-synching her song "Telephone."

Throughout the proceedings, Manning remained outwardly calm while witnesses talked about his emotional problems, his difficulties as a gay soldier during the military's "don't ask, don't tell" era, and his violent outbursts while serving in the United States and then in Iraq from late 2009 to mid-2010.