A Minnesota man accused of helping to recruit and finance U.S. fighters for an overseas terror group heads to trial Monday in a case that's expected to show how some young Somali expatriates in Minneapolis were persuaded to risk their lives for insurgents back home.

Mahamud Said Omar, 46, faces five terror-related counts as part of a much broader investigation into recruiting by al-Shabab, a U.S.-designated terror group at the center of much of the violence in Somalia.

Since 2007, more than 20 young men are believed to have left Minnesota for the East African nation, presumably to take up arms with al-Shabab. The departures shook the Somali community in Minnesota -- the largest in the United States.

While prosecutors don't consider Omar a mastermind in the Minneapolis pipeline, they allege that he was far more than a bit player: They say he encouraged young men to fight, helped some get tickets for travel to Somalia and helped pay for weapons.

"We believe it's a very important case because it will be the government's only opportunity, to date, to explain to the public what has been going on in the Somali community, and how these recruiters have been going after these young men," said U.S. Attorney's Office spokeswoman Jeanne Cooney. "I think it will go a long way in explaining how these cases tie together."

Omar, who came to the U.S. in 1993 and is a permanent resident, insists he is innocent of the charges, which include conspiracy to provide material support to terrorists. He could face life in prison if convicted.

"He maintains that he has never lifted a hand or spoken a word against the interests of the United States, and that's what the evidence will show," said Jon Hopeman, one of Omar's attorneys. "He also has a great respect for the country that took him in."

Eighteen men have been charged in the Minnesota case, but Omar is the first to go to trial. Seven men pleaded guilty, while others are presumed to be out of the country or dead.

A congressional investigation last year put the number of al-Shabab supporters higher, finding that more than 40 people left the U.S. to join the terror group.

Prosecutors say Omar gave money to men who traveled to Somalia in 2007 and went there himself in early 2008. In their account, Omar stayed at a safe house in the city of Marka with other Minnesotans -- including Shirwa Ahmed, who the FBI said was "radicalized" in Minneapolis and would later become the first known U.S. citizen to carry out a suicide bombing.

At the safe house, prosecutors allege, Omar gave provisions to men and discussed training and fighting for al-Shabab. He also is accused of giving hundreds of dollars to fighters so they could buy AK-47 assault rifles.

Omar returned to the U.S. in April 2008 and, prosecutors say, continued to help al-Shabab. He accompanied two travelers to the Minneapolis airport in August 2008.

That November -- days after Ahmed's suicide bombing -- Omar followed the directions of a man in Somalia and helped a group of six men buy airline tickets, accompanied them to the travel agency and gave one traveler money, prosecutors said.

Prosecutors say he also told another man how to get a visa and ticket to Africa and which route was best, according to court documents and transcripts of calls recorded by the FBI.

His brothers, Mohamed Osman and Abdullahi Said Omar, have described their brother as shy and easily led, lacking the brains to be a terrorist and the money to buy weapons.

They say his trip to Somalia in early 2008 was to get married and that he went overseas in November of that year to make the Hajj pilgrimage.

They declined to be interviewed again prior to the trial.

At least initially, many of the Minnesota men appeared to have been motivated by patriotism. In late 2006, Ethiopian soldiers were brought into Somalia by its weak U.N.-backed government, and many Somalis saw that as an invasion. By fall 2007, some were holding secret meetings at Minneapolis mosques and homes, plotting ways to fight the Ethiopians, court documents said.

Prosecutors allege Omar was part of the "secretive plan" to recruit young men to wage jihad against Ethiopians.

Authorities have said early plays on patriotic feelings were eventually supplemented with more radical appeals.

Prosecutors declined to talk about the case as the trial approached, but documents show they plan to call about 25 witnesses, including experts on al-Shabab's methods of recruiting and activities in Somalia, such as five coordinated bombings on a single day in 2008.

Prosecutors also intend to play recordings of phone calls, in which Omar is accused of talking about an "uproar" in Minneapolis, plans for some men to leave the city and the fighting overseas.

At least two men who traveled to Somalia and spent time with al-Shabab are also expected to testify.

Omar's attorneys would not talk about defense strategies. They've ruled out mental disease or insanity as a defense but may ask witnesses to talk about Omar's state of mind. Omar has a history of seizures and nightmares, and told the court he sees ghosts.

One pretrial filing hints that defense attorneys could present evidence about the anti-Ethiopian sentiment among the Somali diaspora, suggesting someone other than Omar might have provided the travelers with money. The defense plans to call Omar's three brothers as witnesses. A decision on whether Omar will testify will be made later.

Abdirizak Bihi, a member of Minnesota's Somali community whose 17-year-old nephew, Burhan Hassan, traveled to Somalia and died there, said the trial is important because it shows "justice is slow, but it's coming."

Prosecutors say Hassan was among the travelers Omar helped.

"Everyone wants to see the details, how (recruiters) do it," Bihi said. "A lot of families are afraid and they want to know what happened so they can be educated in the future and watch out for the young ones."

E.K. Wilson, the FBI supervisory special agent who is heading up the Minneapolis investigation, said Omar's trial is just one piece of a complex, ongoing case.

"It is definitely not the end of the road or the end of the investigation, by any stretch," Wilson said.