Image Mr. Mowen was arrested in Panama after being turned in by other American citizens. His trial is scheduled to start Monday. Credit... Davis County Sheriff's Office

Mr. Mowen, 47, who has pleaded not guilty and remains in custody, faces more than 100 years in prison if convicted of multiple charges, including wire fraud and retaliating against a witness. His lawyer, Stephen R. McCaughey, did not return telephone calls seeking comment.

The federal indictment against Mr. Mowen says that in 2006 and 2007 he promised investors in a foreign currency trading operation returns that might have sounded too good to be true  and, according to the indictment, later turned out to be completely false.

Profits of up to 33 percent a month were paid for a while, the indictment said, but only because new money coming into the fund was used to pay off previous investors, which is the classic definition of a Ponzi scheme.

The dimensions of the case expanded last fall, after Mr. Mowen  arrested in Panama after being recognized and turned in by other United States citizens  was brought back home. From jail, according to a superseding indictment filed against him in November, he enlisted a fellow inmate to kill four prospective witnesses.

Image A motorcycle belonging to Mr. Mowen with a picture of Marilyn Monroe painted on the gas tank. Credit... Ramin Rahimian for The New York Times

But his cars and motorcycles have also been intertwined with the saga from the beginning. According to the indictment, they were bought in part to impress prospective investors with the lifestyle that high-profit currency trading could buy.