INFO:Craig Whitlock

A Navy intelligence official and a California hot-rod mechanic were found guilty Wednesday on federal conspiracy charges stemming from a mysterious scheme to manufacture hundreds of AK-47 rifle silencers for a secret military project.

Lee M. Hall, a civilian Navy intelligence official at the Pentagon, and Mark S. Landersman, the mechanic, were convicted of conspiring to build 349 untraceable silencers — without a firearms license — and shipping them across state lines for a sensitive mission that was never fully explained in court.

U.S. District Judge Leonie M. Brinkema, who delivered the verdicts after bench trials in Alexandria, said she was unconvinced by defense attorneys’ assertions that the silencers were needed for a clandestine purpose and were necessarily obtained outside of normal channels.

“I do not accept the argument that because this might have been covert, that somehow that excuses the participants from playing by the rules,” she said.

Prosecutors had argued that the silencer contract was a $1.6 million sweetheart deal intended to enrich Landersman, a struggling auto mechanic and machinist from Temecula, Calif.

His brother, David W. Landersman, served as Hall’s boss at the Pentagon as the senior director for intelligence in an obscure Navy office. Prosecutors have accused David Landersman of masterminding the contract to help his brother, who had been mired in bankruptcy. He has been labeled an unindicted co-conspirator in the case but has not been charged.

According to trial testimony, Hall and the Landersman brothers went to unusual lengths to conceal the silencer purchase from other Navy officials and contracting representatives. Three Navy officials said they had approved David Landersman’s request to spend the money on intelligence studies, not a weapons deal.

Hall later told another Navy official that the silencers were intended for Navy SEAL Team 6, the elite commando squad that killed Osama bin Laden. But representatives for SEAL Team 6 told agents from the Naval Criminal Investigative Service that they had not ordered the silencers and didn’t know anything about them.

Although the purpose of the silencers was never established, the trial featured a constant undercurrent of intrigue with carefully couched references to classified projects and black operations. Many filings in the case were placed under seal. At the request of military officials, participants at the trial were prohibited from making overt references to the Navy SEALs .

Prosecutors portrayed Mark Landersman as a financially struggling auto mechanic without a federal firearms license who went on a spending binge as soon as he landed the silencer contract, buying fancy cars and investing $100,000 in a microbrewery.

Assistant U.S. Attorney Patricia Haynes said all the talk about classified projects and Navy commandos was “nothing more than a fantasy” concocted to cover up a simple case of fraud.

But defense attorneys cited evidence that Mark Landersman had worked for years to invent new silencer designs for military rifles and had received encouragement from Navy officials who work closely with the SEALs.

Rodney F. Lowell, the weapons accessory manager for the Naval Special Warfare Command, testified that he met with Mark Landersman in 2010 and 2011 to review a silencer prototype for sniper rifles used by the SEALs. Lowell said he thought the prototype was promising but that the Navy didn’t have the money at the time to pay for initial testing.

If funds had been available, Lowell said, “I definitely would have written a check.”

John Zwerling, a defense attorney for Mark Landersman, said he was “very disappointed” by the verdict. During his closing argument, Zwerling said even his client wasn’t told what the silencers would be used for.

“He didn’t know specifically what it was for or where it was going,” Zwerling said. “It was clearly something for black ops.”

Stuart Sears, an attorney for Hall, declined to comment. Both defendants are free on bond until their sentencing hearing Jan. 30. Hall faces up to 15 years in prison and Mark Landersman as much as five years.

Adding to the mystery of the case was the fact that the silencers were designed to fit Russian-made AK-47 automatic rifles, not standard-issue U.S. military weapons.

Prosecutors and a weapons tester for the Navy described the silencers as shoddily made, poorly designed and of limited use. According to testimony, the silencers only cost $10,000 in parts and labor to manufacture but were sold to the government for more than $1.6 million.

Defense attorneys said the price was reasonable because Mark Landersman had spent years working on the design. They also hinted that the silencers’ poor performance was exactly why the Navy ordered them — suggesting obliquely that they were destined to end up in the hands of foreign guerrillas who may or may not have been friends of the United States.

Sorting out the truth of the case has been made even more challenging because of the destruction of potential evidence.

Navy security officers testified that they incinerated documents last year that had been seized from the offices of Hall and David Landersman — three days after The Washington Post published a front-page article about the unfolding investigation. Defense attorneys also accused the Navy of destroying a secret stash of automatic weapons that the silencers were designed to fit.

The Navy has placed Hall in a “non-pay status” as it weighs “the appropriate personnel action to be taken” as a result of his conviction, said Cmdr. Ryan Perry, a Navy spokesman. Perry said the Navy was pleased that the NCIS had “uncovered this criminal activity and investigated it to the fullest,” adding that the Navy “will make any necessary improvements to ensure this type of activity will not recur.”