Even among the colourful pantheon of Texas lawmen, Hudspeth County Sheriff Arvin West has seized his share of the limelight. In his 16-year career patrolling the West Texas outback, he has busted crooner Willie Nelson for pot, accused the Mexican army of invading US territory and repeatedly ripped the federal government on television over border security.

Less well known are the country sheriff’s strange connections to a rogue Navy intelligence office at the Pentagon that has been under criminal investigation for the past three years.

The former director of the intelligence unit, David W Landersman, a civilian, is facing federal conspiracy charges for allegedly orchestrating a mysterious scheme to equip Navy commandos with hundreds of untraceable AK-47 rifle silencers.

A new wrinkle in the case, however, has recently emerged in US District Court in Alexandria, Va., where prosecutors have suggested that Navy officials from the intelligence unit also sought to funnel military equipment to rural Hudspeth County and set up a secret training base near the Mexican border.

Even more unusually, two of Landersman’s former subordinates have testified that when they were not working full time on intelligence matters at the Pentagon, they moonlighted 1,600 miles away as reserve deputy sheriffs in Hudspeth County, a desolate, Connecticut-size jurisdiction east of El Paso.

Also serving as deputies to Sheriff West were Landersman, his son, and the husband of one of the Navy intelligence officials, according to two Pentagon officials and others familiar with the case.

Why so many Pentagon officials and their relatives were working on the side as sheriff’s deputies in Texas has not been explained in court, where much of the evidence has been sealed to protect national security. What a training base would have been used for there is just as murky.

West, who was first elected as Hudspeth County sheriff in 2000, did not respond to several phone calls and emails seeking comment. He has not been charged with any wrongdoing.

Hudspeth County is home to only 3,300 people but covers an enormous stretch of parched terrain in the Rio Grande basin. It is best known for a Border Patrol checkpoint on Interstate 10 where drug-sniffing dogs nab hundreds of motorists a year for carrying small amounts of marijuana.

Besides Nelson, other musical performers who have been arrested on drug charges while passing through Hudspeth County include Snoop Dogg, Fiona Apple and Nelly.

West, who has been described by NPR as “a stout, swaggering lawman” with a sign over his office that reads “Boss Hog,” has just 14 full-time deputies under his command. To compensate, he has sometimes recruited outsiders to provide extra muscle.

In 2011, he pinned a reserve deputy sheriff’s badge on Hollywood tough guy Steven Seagal. Insisting the move was not a publicity stunt, West predicted the action star would bring “a wealth of tactical experience and dedication as a peace officer” and teach martial arts to others in the department.

Exactly what the Pentagon officials did during their stints as deputy sheriffs in Hudspeth County remains unknown. But apparently the work could be dangerous.

Worried about threats from Mexican drug lords, West required his special deputies to carry a firearm for self-protection when they flew on commercial airlines, according to Sterling Gill, a civilian Navy official who served in Hudspeth County.

The policy even applied when they traveled outside Texas. At a court hearing this September, Gill testified she once carried a gun on a flight between Washington and San Francisco.

“My sheriff, who has had several threats against his life by the drug cartel and has a bounty on his head, insists that all of his deputies fly armed at all times,” Gill added, noting that she filled out the proper paperwork to carry a weapon on board.

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Gill holds personal ties to Hudspeth County through the 32,000-acre Circle Ranch, a property owned by her in-laws. At the court hearing, she acknowledged that Landersman — her boss at the Pentagon and a fellow onetime Marine — had visited the ranch on at least four occasions.

In a brief line of questioning, prosecutors asked Gill whether she and Landersman had tried to set up a military training centre at the ranch, along with new roads, an airstrip and $14,000 worth of radios from the Defense Department.

Gill said the radios were intended for the Hudspeth County Sheriff’s Office. She denied the other allegations without elaborating.

Gill has not been charged in the case. She testified that the Navy has suspended her indefinitely without pay and that she is under investigation by the Naval Criminal Investigative Service (NCIS). Her attorney, Christopher Man, said Justice Department officials have told him it is unlikely they will bring charges. He declined further comment.

The Texas connection represents another puzzle in an already enigmatic case involving the Navy intelligence unit.

Blandly known as the Office of Plans, Policy, Oversight and Integration, the small agency has about 10 people on staff, mostly civilians, and is supposed to focus on policy matters. Somewhere along the way, however, it started to become more directly involved in secret missions, prompting one former senior Navy official to describe the group as “wannabe spook-cops.”

The office came under scrutiny in January 2013 when one of its civilian executives appeared at a Defense Intelligence Agency office in Arlington, Virginia, and asked for a badge that would allow him to carry weapons on military property, according to prosecutors.

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The executive flashed a set of credentials stamped with the letters LEO — an acronym for “law enforcement officer” — even though he lacked police powers. That prompted federal agents to search his office at the Pentagon, where they found more suspicious badge materials.

The investigation broadened as NCIS agents uncovered evidence that the intelligence unit had arranged an unauthorized, sweetheart contract to purchase AK-47 silencers from Landersman’s brother, Mark, a California hot-rod mechanic.

Under terms of the deal, Mark Landersman produced a batch of 349 homemade, unmarked silencers in a machine shop and sold them to the Navy for $1.6 million, even though they cost only $10,000 in parts and labour to make.

After a federal trial, Mark Landersman was convicted of conspiracy in October 2014 along with a Navy intelligence official who helped arrange the contract, Lee M. Hall. Both men are appealing the verdicts.

The silencers’ intended use remains hazy. Many details are classified, but some court filings suggest they were part of a top-secret operation to help arm Navy SEAL Team 6, the unit that killed Osama bin Laden.

David Landersman, who was indicted after his brother’s conviction, has pleaded not guilty. His attorney has argued that the intelligence-unit director was kept in the dark about the contract between his brother and the Navy and that a subordinate orchestrated the deal without his knowledge.

Adding to the air of mystery have been revelations in court that Navy security officials burned and shredded piles of sensitive documents shortly after The Washington Post first reported on the existence of the investigation in November 2013.

David Landersman’s attorneys have argued that the case against their client should be thrown out because the destroyed files would show that other Navy officials oversaw the silencer contract.

They have hinted that Navy officials also wanted to get rid of the documents because they contained other embarrassing information, including notes about sexual misconduct at the Pentagon and files related to a massive bribery investigation into the Navy’s 7th Fleet.

Richard Kent Ford, the Navy security officer who supervised the destruction of documents, has said that he was purging old files in accordance with Navy regulations. He originally testified in 2014 that he was unaware that Landersman, Gill and others from the intelligence unit were under investigation or that there had been news coverage of the case.

At a court hearing this September, however, Landersman’s attorneys confronted Ford with an email Ford had written alerting several Navy officials to The Post’s front-page article shortly before he oversaw the elimination of the files.

“He lied to this court straight up,” said Stephen M. Ryan, one of Landersman’s defense lawyers, adding that Navy officials had demonstrated “more than a whiff of bad intent” by destroying evidence.

Ford denied lying on the stand, saying he had forgotten about The Post’s coverage. Records from a separate personnel hearing, however, show that the Navy booted Ford from his job after concluding he was “not truthful” in his original testimony in the silencer case.

Justice Department officials said that Navy security officers destroyed the documents without their knowledge. They also argued that the files were not relevant to the case.

US District Judge Leonie M. Brinkema is scheduled to rule whether to dismiss the charges against Landersman or proceed to trial. “It’s certainly a messier-than-normal case,” she said at a hearing.