By prosecutors’ account, Jeffrey A. Sterling was a man with an ax to grind. Upset over losses in his legal squabbles with the CIA, they argued, the former officer leaked classified details to a reporter about an important program to learn about and deter Iran’s nuclear ambitions.

But the way his defense attorneys tell it, Sterling, 47, was a “patriot” who joined the CIA because he loved his country. They argued that he never told any unauthorized person about his clandestine work for the U.S. government, and they suggested that there were a few other people who might not have been so honest.

With those opening salvos, the two sides kicked off the criminal leak case against Sterling on Tuesday in federal court in Alexandria — a years-in-the-making trial that promises to serve as a reminder of how aggressively the Obama administration has pursued alleged leakers.

The proceedings, even on day one, were shrouded in intrigue. Several witnesses — CIA employees — testified using only their first names and last initials, and were shielded by a screen that ran most of the width of the courtroom. One talked of flashing a suitcase containing $50,000 to entice a man to cooperate with the agency.

Jurors will have to decide whether Sterling gave classified material to New York Times reporter James Risen for his 2006 book “State of War” and whether that disclosure included secret national security information. At issue in particular is a chapter about an operation, which Risen described as botched, that was meant to sabotage Iran’s nuclear plans.

On Tuesday, Assistant U.S. Attorney James Trump said that reading the chapter in question was powerful evidence against Sterling. He said that Risen’s view of the secret operation was incomplete and that the only person who had access to just the sphere of information that Risen reported was Sterling.

Trump argued that Risen had quoted Sterling in an unrelated article about Sterling’s discrimination lawsuit against the CIA and that the two men exchanged phone calls and e-mails. He said that when Sterling ultimately detailed concerns about the operation to the Senate Select Committee on Intelligence, his descriptions contained the “same spin” that would later appear in Risen’s book.

Trump said Sterling was “bitter, he was angry, he was seeking revenge.”

Trump also defended the general worth of the operation — an effort by CIA personnel to have a Russian scientist, referred to in court only as “Merlin,” give flawed nuclear plans to Iran. Trump rejected reporting by Risen that indicated that the operation perhaps aided Iran. He argued that the writer’s revelations hurt the CIA’s ability to recruit people to help with secret missions. At least two CIA officers testified that Merlin was a valuable CIA “asset.”

Edward B. MacMahon Jr., Sterling’s attorney, said his client was caught in a “food fight” between the CIA and Risen. He said prosecutors had no direct evidence linking any leaks to his client and suggested that there were other people who possibly could be Ri­sen’s sources.

Risen will not testify at the hearing. He vigorously fought the Justice Department’s effort to subpoena him, and — although he lost in court — generated enough public outcry to persuade Attorney General Eric H. Holder Jr. to back down. Jurors will hear portions of a transcript from a previous hearing at which Risen testified, and MacMahon noted Tuesday that Risen spoke then of having a “wide range” of sources.

Risen and his lawyer did not respond to e-mails seeking comment Tuesday. The trial is expected to run until the end of January.