Plaintiffs' attorneys Lin Wood and Marlan Wilbanks, who claim DaVita made as much as $800 million over-billing the government, say that DaVita's defense won't hold up in court.

"It's not just the taxpayers that are the victims here, it's the health care system," Wood said.

"It doesn't take a graduate degree to understand what's going on here," Wilbanks said. "This is just dishonesty."

DaVita denies that and vows to fight the case in court. But earlier this year, while denying it did anything wrong, DaVita settled a similar case in Texas for $55 million.

Pat Burns, with the watchdog group "Taxpayers Against Fraud," says the bigger problem is that even if a company gets caught cheating the government, the company executives never seem to face any punishment. Fines are paid and business continues as usual.

"The way it's set up right now, if the fraud is not caught, then taxpayers foot the bill, Burns said. "If the fraud is caught, stockholders foot the bill."

Burns and others have been arguing for much harsher treatment when companies are found guilty of defrauding the federal government. He points to record billion-dollar fines, particularly in the pharmaceutical business, that are paid, but executives don't get punished and the companies continue to do business with the government.

In fact, one of DaVita's defenses to CNN is that the federal government itself declined to charge the company with wrongdoing, even after reviewing the fraud allegations.

"The government has come in and thoroughly investigated what the allegations are, and in both cases the government decided to drop it and move on," Rivera said.

Federal prosecutors in Georgia declined to intervene in the case but stated in a letter that decision "should not be construed as a statement about the merits of the case."

The short-staffed U.S. Department of Justice declines to join lawsuits all the time, instead allowing private citizens who hire private lawyers to essentially prosecute for the government, Burns said.

"The U.S. Department of Justice simply doesn't have the people," Burns said. "It should have the people. I think we all would agree to that. It simply doesn't."

Which brings us back to the original meeting of one doctor and one nurse who now stand to make millions if these allegations of fraud are proven true.

The biggest winners, though, in their lawsuit could be taxpayers. The U.S. government will recover the bulk of whatever they win. They and others like them are essentially the U.S. taxpayers' deputies in the fight against health care fraud. Asked if they are surprised that they have to defend the U.S. taxpayer, Barbir said simply, "I'm not surprised. It's not easy to come forward and stand up and tell the truth, but it's the right thing to do."

The case is set for trial later next year.