A federal criminal trial in Alexandria, Va., is examining the purchase of unmarked rifle silencers by a little-known Navy intelligence office at the Pentagon. (AFP/Getty Images)

Witnesses, attorneys and even the judge took special care not to let the phrase “Navy SEALs” pass their lips during a federal criminal trial in Alexandria this week, further cloaking an already mysterious case involving the purchase of hundreds of unmarked rifle silencers for the military.

Instead, people involved in the trial referred obliquely to “the program,” “operators” and “other entities in the government” when discussing who might have wanted to use the silencers, which were acquired through a classified Navy contract.

On Wednesday, a key defense witness was interrupted almost immediately after he introduced himself as the weapons accessory manager for the Naval Special Warfare Command — which oversees the Navy’s commando units, including the furtive SEALs.

“Has it been explained to you that certain terms are not to be used?” U.S. District Court Judge Leonie M. Brinkema cautioned. The witness, Rodney F. Lowell, replied that he had been advised of the restrictions, but noted that the name of the Navy command itself was hardly a secret.

The case centers on charges that a civilian Navy intelligence official, Lee M. Hall, conspired to steer a hugely profitable $1.6 million contract to a recently bankrupt California auto mechanic to make 349 silencers. The devices were designed to fit AK-47-style automatic rifles — not standard U.S. military weapons — and lacked any markings or serial numbers.

The mechanic, Mark Landersman, is the brother of Hall’s boss at the Pentagon. According to testimony and records in the case, he spent less than $10,000 in parts and labor to manufacture the batch of silencers.

During three days of testimony that ended Wednesday, both sides shied away from answering why the silencers were made in the first place and for whom they may have been intended, apparently heeding requests from the military to protect official secrets.

According to one document filed last year by prosecutors, Hall told a government witness during a recorded phone call that the silencers were designed for the Naval Special Warfare Development Group. That’s the formal name for SEAL Team Six — the elite commando unit that killed Osama bin Laden.

In later filings, however, prosecutors scrubbed all references to SEAL Team Six. They also redacted all mentions of the group when the recorded phone call was played in court. During one uncensored portion of the call, Hall said the recipients of the silencers “are going to use them for what they do for a living.”

Prosecutors said there was no evidence that any Navy forces had actually asked for or needed the silencers. They also cited testimony from a Navy weapons expert that the silencers had failed several performance tests and were made out of cheap aluminum instead of stainless steel.

The silencers were “unwanted, unneeded and ineffective,” Patricia Haynes, an assistant U.S. attorney, said during her closing argument. “U.S. taxpayers are now out nearly $2 million for suppressors that are basically scrap metal.”

Hall’s attorneys said he believed there was a legitimate need for the silencers. Although they could not provide any written documentation to that effect, they said their hands were tied because of the sensitive nature of the work that Hall did.

“There was a program related to this purchase,” said Danny Onorato, one of the defense lawyers, adding that he was “barely able to talk about” it in court.

“I don’t know how we could ever get a fair trial,” he said. “The deck is stacked when you’re talking about classified information.”

Brinkema, the judge, said she will render a verdict in the coming days.

Landersman is scheduled to go on trial Monday. His brother, David Landersman, the Navy’s senior civilian director for intelligence, has not been charged; prosecutors have referred to him as an unindicted co-conspirator.