Being an informant for the FBI in the Fort Dix terror investigation has paid well, a witness explained to jurors Monday.

John Stermel, an investigator assigned to an FBI counterterrorism task force, spent Monday morning on the stand detailing the role of informant Mahmoud Omar, who wore a wire for 16 months in the investigation of five men accused of planning to shoot soldiers at the Army training base.

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Omar was set to testify next — though that might not begin until Tuesday.

Defense lawyers say it was Omar who tried to plot an attack — not their clients. No attack happened.

Omar will have received some $185,000 in payments by year's end, plus reimbursement for $25,000 in expenses and nearly $29,000 in rent, Stermelo testified.

Weekly payments of $1,500 began in August 2006, the month Omar went with one of the defendants, Mohamad Shnewer, to check out Fort Dix and other military installations in New Jersey, Delaware and Pennsylvania, Stermel said.

The government also has paid the former used car salesman's $1,400-a-month rent since someone working for a defense lawyer in the case tracked him down more than a year ago, Stermel said.

Stermel said Omar's help also has led to three criminal convictions on fraud cases unrelated to the alleged Fort Dix plot.

Anticipating defense attacks on Omar's credibility, a prosecutor asked Stermel about Omar's missteps. Among them: He tested positive for marijuana once while on probation; he admitted selling a Social Security number and was caught in a bank fraud case for which he has not been prosecuted.

The defendants — all foreign-born Muslims in their 20s who spent years in Cherry Hill — are all charged with conspiracy to kill military personnel and attempted murder.