In opening arguments in the trial on Oct. 20, defense lawyers made it clear that they would go after Omar, questioning his motive for helping the government and suggesting that his involvement was a professional scam artist's way of scamming the government.
"The FBI was chasing him before," said Rocco Cipparone, the lawyer for suspect Mohamad Shnewer. "And now, they're paying him."
Omar, a native of Egypt who speaks broken English, came on the radar of law enforcement in 2001. That's when he was indicted and charged with four other men in a scheme to open bank accounts around Pennsylvania, deposit counterfeit checks, then cash them before the banks caught on.
Three months after he was arrested, Omar agreed to help the government. Instead of facing a maximum penalty of 30 years in prison, he was sentenced to six months behind bars.
On the witness stand in that case, Omar admitted that he had double-crossed the ringleader. He agreed to split proceeds of the fraud with him, but said he never did.
He has been a central figure in the Fort Dix case almost since the beginning.
The Fort Dix terror plot investigation began in January 2006, after a clerk at a Circuit City store in the Philadelphia suburb of Mount Laurel told police about a video that troubled him when he was asked by a customer to convert it to DVD. Along with scenes of men skiing and riding snowmobiles, it also showed several men firing guns and shouting "Allah akbar." That Arabic phrase, which means "God is great," is also heard repeatedly in jihadist videos.
The FBI brought Omar into the case in March 2006.
By the end of this year, lawyers say, he will have been paid $238,000 for his work. While he worked for the government, he moved from a downmarket apartment in Paulsboro to a middle-class one in Cherry Hill, not far from where four of the suspects lived.
His job was to infiltrate the group. He focused mostly on Shnewer, who was then a few months shy of 21. Shnewer was a community college student who worked sometimes at his family's small grocery store in Pennsauken.
Omar, now 39, became a regular customer there and got to know the younger man, whom Shnewer's own lawyer describes as the butt of his friends' jokes.
For more than a year, Omar wore a wire and recorded hundreds of hours of conversations with Shnewer and the others.
His house and car were both rigged with hidden cameras at times to capture the suspects' words and actions.
The jurors certainly will hear snippets of many of those conversations.
Defense lawyers say they will show him trying to pull the suspects into an attack plan to make it appear there's a conspiracy.
Prosecutors will say that they simply show a conspiracy. In his opening arguments last week, Deputy U.S. Attorney William Fitzpatrick told jurors, "The FBI in this case exposed a crime. They did not create one."
Omar's life will also be scrutinized when he's on the witness stand.
In opening arguments, Fitzpatrick braced for that, acknowledging that Omar and a second paid informant, Besnik Bakalli, are not model citizens. But Fitzpatrick said that to get the goods on the alleged plotters, investigators needed an informant who would be credible to them.
Defense lawyers say they'll show that Omar had a drug problem and that he was often involved in enterprises that range from sketchy to illegal.
For instance, they say he supported himself by buying, fixing and reselling cars - including cutting some into pieces and shipping them to Egypt to be reassembled and sold there. Some of those cars may have been stolen, Cipparone said.
The defense lawyers also say that Omar sold his Social Security card for $3,000 while working for the FBI. They told jurors that when the FBI found out about it, agents agreed to look the other way.
The conversations that have been made public so far have a running theme of Omar talking about buying forklifts or helping others in the case buy cars.
So far, the jury has been shown just one video involving Omar - the last one, made on May 7, 2007.
In it, two of the suspects visit Omar's apartment in Cherry Hill to buy seven AK-47 and M16 machine guns. Omar says they were supplied by a dealer he knows from Baltimore. The guns were really supplied by the FBI, which had a SWAT team positioned in the next apartment.
The video lasts only about seven minutes before the screen goes black and agents can be heard storming in to arrest the men.
Over the next few hours, five men - all foreign-born Muslims in their 20s who had spent years in Cherry Hill - were arrested in the plot. They are being tried for conspiracy to murder uniformed military personnel, attempted murder and weapons offenses.
It's not clear where Omar has been since the arrests. But they took place just a few weeks after his probation ended in the bank fraud case - meaning he was legally free to leave the country.
District Court site with trial evidence: http://www.njd.uscourts.gov/FortDixTrial/index.html