An unusual federal trial spotlighting a global prescription pill enterprise and a mysterious international crime boss took a surprise turn Monday when a judge in St. Paul abruptly acquitted two of the four defendants, saying prosecutors had produced "simply a dearth of evidence."

Defense attorneys in the case were prepared to call Paul Le Roux, a shadowy figure who once coolly admitted having a role in more than a half-dozen murders around the globe. They expected Le Roux to testify as part of "duress" defenses, arguing that their clients worked for his RX Limited online pill business because they feared for their lives.

But after 18 days of trial in St. Paul, defense lawyers concluded that the prosecution — led by attorneys from the Justice Department's consumer protection division in Washington, D.C. — hadn't built a strong enough case to proceed.

U.S. District Judge Susan Richard Nelson agreed, acquitting defendants Moran Oz and Lachlan McConnell and concluding that even the most persuasive testimony elicited by prosecutors didn't "clear the hurdle of reasonable doubt."

The decision means that Le Roux, who was flown from New York to be held in Minnesota's Oak Park Heights prison during the trial, is not likely to testify. Le Roux has been in federal custody since being arrested in Liberia in 2012 and striking a plea agreement with the government.

Attorneys for Oz, a 33-year-old Israeli national, planned to ask Le Roux about an incident in which his associates allegedly threw Oz from a boat into open water and shot at him. McConnell, a Canadian citizen who worked security for Le Roux's businesses, said it was made clear to him that he could be killed if he wasn't considered useful to his boss.

"We had a compelling story to tell," said Robert Richman, one of Oz's two attorneys, who moved for acquittal after prosecutors completed their case Friday. "At the same time we felt there was tremendous strength in telling the jury there's not one thing the government said that we felt the need to rebut."

Justice Department officials on Monday declined to comment.

Both McConnell, 58, and Oz plan to return to their home countries later this week, attorneys said. Two other co-defendants, Drs. Elias Karkalas and Prabhakara Tumpati, still face charges after Nelson declined their lawyers' motions for acquittal.

Reading a preview of her ruling early Monday, Nelson said prosecutors failed to prove that Oz or McConnell conspired to commit any crimes, were aware of a conspiracy or took any steps to conceal their activity. As it became clear that Oz would be released, his wife rocked back and forth in the courtroom gallery, sobbing. "I'm just glad after three years that it's over," Yamit Oz said later outside the courtroom.

In a phone interview later Monday, Oz described that period as a "nightmare."

"It's like the movies," Oz said. "They got the wrong person."

Oz helped manage a call center in Israel and McConnell worked security for Le Roux's businesses before assisting RX Limited in the United States. Prosecutors said the business generated sales of more than $200 million in prescription drugs delivered without valid doctor-patient relationships or physical examinations.

Those earnings helped fund Le Roux's other illicit enterprises, including gunrunning in the Philippines and arming a militia in Somalia, attorneys said.

Speaking after Monday's ruling, McConnell said he suspected Le Roux's deep pockets helped buy favor from authorities overseas. This proved worrisome when, after one of McConnell's peers was killed, Le Roux told McConnell that he was still alive only because the boss still needed his services.

"Basically I felt that if he didn't need me I would have been killed too," McConnell said.

Le Roux has not been sentenced under his plea agreement and is being held under witness protection, attorneys said.

Ryan Pacyga, one of McConnell's attorneys, told jurors at the trial's outset that the "government made a deal with the devil." He and other attorneys involved in the case called the government's approach — using a kingpin to help bring charges against defendants down the chain — unusual.

"To make your case based on the worst man in the world and not call him as a witness — once they got Le Roux, there should not have been a case," said Joe Friedberg, an attorney for Oz.

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