ALEXANDRIA, Va. — A business associate of the former national security adviser Michael T. Flynn was convicted on Tuesday in Northern Virginia of secretly lobbying for Turkey, a victory for the government after the judge considered dismissing the case because prosecutors lacked evidence.

Judge Anthony J. Trenga had described the evidence against Mr. Flynn’s associate, Bijan Kian, as speculative and very circumstantial but let the case go to the jury. Judge Trenga could still toss the verdict and scheduled a Sept. 5 hearing on the matter.

During the short trial in federal court in Alexandria, Va., prosecutors had accused Mr. Kian and his business partners of trying to “subvert the American process” when they secretly agreed to work for Turkey. They said that Mr. Kian was operating at Turkey’s control and direction.

Mr. Kian’s defense lawyers repeatedly tried to undercut the government’s case, saying there was no actual agreement with the Turkish government to influence American policy. Prosecutors, Mr. Kian’s lawyers said, could not even demonstrate that Turkey paid for anything.