A one-time candidate whose suspicious campaign finances led to an FBI investigation of former Miami Congressman David Rivera was formally charged Friday in federal court with three crimes.

Shackled at the wrists, waist and feet, Justin Lamar Sternad pleaded not guilty to conspiracy, false-statement and illegal campaign-contribution charges.

Sternad is expected to strike a plea deal as he cooperates with federal authorities in their investigation of Rivera and the former representative’s close friend, Ana Alliegro, who managed Sternad’s disastrous Democratic primary campaign for a Kendall-to-Key West congressional seat.

Neither Rivera nor Alliegro is listed by name in the 10-page federal charging document, which lists Sternad’s nameless “co-conspirators” as hand-delivering stacks of cash and checks to campaign vendors.

In all, Sternad received at least $81,486 in unreported cash and checks in less than three months last summer, the charging document said. The money helped pay for some fliers that attacked a Democratic rival of Rivera, a Republican. “This was a message to Rivera. It’s a preview of what the indictment against Rivera will look like,” David S. Weinstein, who once led federal public-corruption prosecutions in the Southern District of Florida, told The Miami Herald and El Nuevo Herald after reviewing the case.

Rivera, who has maintained his innocence, refused comment but pointed to past statements in which he said he never has been informed by authorities of a federal investigation.

Weinstein pointed out that the charging document indicates prosecutors are hunting for a “big fish.” A sign of Sternad’s cooperation: He was charged by an “information” sheet filed directly by prosecutors, instead of an indictment by a grand jury.

The charging information against Sternad is about three times longer than typical information sheets and is filled with details — check numbers, bank account names, dates of transactions — that telegraph what Rivera is facing, Weinstein said.

Sternad faces a maximum five years imprisonment and $250,000 for each count, but he’ll probably get a far lighter sentence, Weinstein said, noting that the defendant could have faced more serious money-laundering charges.

“Sternad is clearly talking. He’s telling what happened and what he knows,” Weinstein said. “If this was a standard information, and not a shot across the bow at Rivera, this wouldn’t have all the detail you see.”

But, Weinstein said, Rivera could prove tough to prosecute because Alliegro’s whereabouts are unclear. She was supposed to meet with FBI agents in September, but she skipped out and initially disappeared. Lawyer Mauricio Padillo, who attended Sternad’s hearing, said he couldn’t comment about his client.

Sternad’s attorney, Enrique “Rick” Yabor, declined to comment.

Rivera has said he never met Sternad, a political newcomer and night-time hotel worker who lives in Cutler Bay.

The federal document also shows that a printing company with long ties to Rivera, Expert Printing & Graphics in Doral, played a central role in the alleged conspiracy when it both received cash and checks and paid another vendor on Sternad’s behalf. Enrique “Henry” Barrios, vice president of Expert Printing, runs the only named campaign vendor in the case whose officials have refused to comment to The Herald.