WASHINGTON - When U.S. Army Pfc. Bradley Manning walks into a military court Friday in Maryland, his many supporters and detractors will get their first glimpse of the soft-spoken Oklahoma native since his arrest in Iraq 19 months ago.

Manning is the only person charged with unauthorized release of more than half a million classified U.S. military reports and diplomatic cables from around the globe, as well as a 2007 video of a deadly U.S. helicopter attack in Baghdad, to the WikiLeaks website.

Supporters see Manning as a whistle-blower who helped expose U.S. military misdeeds and energize protests against corrupt regimes. Critics condemn him as a villain who did immeasurable harm to U.S. troops and allies while America was at war.

He has pleaded not guilty to charges of aiding the enemy, transmitting national defense information in violation of the Espionage Act, and more than 20 other criminal charges. If convicted, he could be sentenced to life in a military prison.

His supporters will call for his release at a protest rally at Fort Meade, Md., where his hearing is scheduled. Other demonstrations are planned this weekend in London, New York, and Washington.

Called an Article 32 hearing, the military proceedings are similar to a grand jury in the civilian justice system and may last a week or more. The presiding officer will recommend whether reasonable cause exists to proceed with a full court-martial.

"The bar is pretty low" for the case to move to trial, said Philip Cave, a retired Navy judge advocate who works in military courts as a civilian lawyer.

Manning, who turns 24 on Saturday, was an intelligence analyst in Iraq. He had a top-secret security clearance and access to the Secret Internet Protocol Router Network, or SIPRNet, which is used by the U.S. government to transmit classified information. Prosecutors say he downloaded a vast haul of material from SIPRNet to his private computer, then passed it to WikiLeaks.

The material included several hundred thousand Army reports from Afghanistan and Iraq, some of which revealed civilian deaths not previously reported. Some reports identified secret intelligence sources, and publication may have put their lives in danger, U.S. officials said.

Also released were more than 250,000 diplomatic cables from U.S. embassies around the world. Some included candid but embarrassing descriptions of foreign leaders, or revealed details of government corruption.

Protesters in Tunisia and Egypt cited the U.S. cables as proof of regime corruption during the Arab Spring uprisings earlier this year.

WikiLeaks founder Julian Assange, 40, is fighting extradition from Britain to Sweden to face allegations of sexual assault, which he contends are a pretext to send him to the United States to be prosecuted for the leaks. Assange is not known to have been charged under U.S. law.

Court documents indicate Manning's lawyers will try to show that officials exaggerated damage to U.S. security caused by the leaks, that the Army did not follow procedures for securing classified information, and that the Army ignored signs that Manning suffered from mental-health problems that may have made him a security risk.

His lawyers told the court they may seek to call 48 defense witnesses, including high-profile figures, during the hearing. It is unlikely that senior U.S. officials will be compelled to testify, legal experts say.

Manning lawyer David E. Coombs has asked that former Defense Secretary Robert M. Gates and Secretary of State Hillary Rodham Clinton testify about the impact of the disclosures, and wants President Obama to testify about comments he made to a Manning supporter in April.

"We're a nation of laws. We don't individually make our own decisions about how the laws operate. . . . He [Manning] broke the law," Obama said, according to a video of the exchange posted on YouTube. Coombs is expected to argue that Obama, as commander in chief, prejudiced any potential jury and made a fair trial impossible.

A soldier who served with Manning's unit in Iraq is expected to testify to Manning's "extreme emotional issues" and say that in 2009 he found Manning "curled in the fetal position in the brigade conference room, rocking himself back and forth," according to court documents. The names of witnesses are redacted on the public documents. Army psychological evaluations of Manning in 2009 and 2010 concluded he was a risk to himself, according to defense documents, but his security clearance was not changed.

Some legal experts say the case shows how far the government will go to protect classified information.

"The number and the nature of the charges against [Manning] are overkill," said Elizabeth Goitein, an expert on secrecy at the New York University School of Law. The broader problem, she added, is that the government classifies too much information.