While he was Maryland's chief federal prosecutor, Deputy Attorney General Rod Rosenstein's office failed to interview the undercover informant in the FBI's Russian nuclear bribery case before it filed criminal charges in the case in 2014, officials told The Hill.

And the prosecutors did not let a grand jury hear from the paid informant before it handed up an indictment portraying him as a "victim" of the Russian corruption scheme or fully review his extensive trove of documents until months later, the officials confirmed.

The decisions backfired after prosecutors conducted more extensive debriefings of William Campbell in 2015, learning much more about the extent of his undercover activities and the transactions he engaged in while under the FBI's direction, the officials said.

The debriefings forced prosecutors to recast their entire criminal case against former Russian uranium industry executive Vadim Mikerinn - removing the informant as a star witness and main victim for the prosecution, the officials added.

Justice Department officials began briefing Congress last week, divulging missteps in a case that nonetheless proved the Russian state-owned Rosatom was engaged in criminal activity through its top American executive beginning in 2009, well before the Obama administration made a series of favorable decisions benefitting Moscow's nuclear giant.

Multiple House and Senate committees already are investigating whether the FBI alerted President Obama or his top aides to the Russian criminal activity and plan to interview the undercover informant soon.

The new revelations, however, could tip some scrutiny toward federal prosecutors' own conduct in the case, a sensitive topic since Rosenstein is now Justice's No. 2 official and the supervisor of the special counsel investigation into Russian election tampering.

Harvard law professor Alan Dershowitz said it was troubling that prosecutors would ever bring a case without talking first to a person they portrayed in court as a victim, especially when that person was an FBI informant available to them.

"I've never heard of such a case unless the victim is dead. I've never heard of prosecutors making a major case and not talking to the victim before you made it, especially when he was available to them through the FBI," Dershowitz said.

"It is negligence, and I'm sure there will be internal issues with the Justice Department and U.S. attorney for making such an obvious mistake," he said.

Officials told The Hill that prosecutors working for Rosenstein first interviewed Campbell, the informant, after they had already filed a sealed criminal complaint against Mikerin in July 2014.

Campbell got one debriefing after the criminal charges were filed, but was never brought before the grand jury that indicted the Russian figure in November 2014 even though the informer was portrayed as "Victim One" in that indictment, the officials confirmed

When prosecutors finally interviewed Campbell more extensively in early 2015 and reviewed all of the records he had gathered for the FBI, they learned new information about the sequence of transactions he conducted while under the FBI's supervision, as well as the extensive nature of his counterintelligence work for the U.S. government that went far beyond the Mikerin case and dated to at least 2006, the officials said.

"Based on what was learned, we decided to change the theory of the case. ... A plea deal became our goal so we wouldn't have to litigate or make an issue of some of the stuff he had done for [counterintelligence] purposes," a source directly familiar with the case said.

Campbell's lawyer, Victoria Toensing, confirmed the Justice officials' account. "The first time Mr. Campbell was interviewed by the U.S. Attorney's office was after the criminal complaint was filed, and he was never brought before the grand jury before the indictment," she told The Hill.

Justice officials said they knew when they first brought the case that Campbell had been part of a controlled, FBI-authorized bribery scheme, meaning he had permission to make payments to the Russians as kickbacks to further the investigation.

They declined to say why, with that knowledge, they initially portrayed Campbell in the indictment as a "victim" of an extortion scheme that began in November 2009 when the FBI had authorized him to make regular kickback payments of $50,000 in order to keep his consulting work for the Russians.

They said, however, they decided to pivot the case from extortion to money laundering after the more extensive 2015 debriefings revealed other transactions that pre-dated the extortion charges.

One source familiar with the case said extortion felt like a weaker charge when Campbell was acting with the FBI's blessing and that the evidence of money laundering that Campbell documented through secret accounts in Latvia and Cyprus was irrefutable.

Campbell, who now has leukemia, also suffered an earlier bout with cancer in the middle of the case when a lesion was detected on his brain. He survived, all the while working undercover, but he developed some memory issues after treatment, sources said.

To compensate, he developed a system of extensive note taking and documentation with his FBI handlers through email to ensure facts were captured before his memory became hazy. A lot of those notes did not get reviewed by prosecutors until 2015, well after charges were filed, the sources said.

The documentation shows Campbell's work had exposed wide-ranging details about Russia's nuclear activities across the globe, including efforts to corner the global uranium market, assist Iranian nuclear ambitions and to criminally compromise a U.S. trucking firm that transported Russia's nuclear fuel, they said.

Officials said the investigation and Campbell's work from 2006 to 2013 fell under the FBI's counterintelligence arm and Justice's national security division, and officials originally did not intend for it to become a criminal case.

Justice officials originally hoped they simply could use the threat of criminal prosecution to "flip" Mikerin as a cooperating asset, but their confrontation with him at an office building in 2014 failed to persuade him to cooperate, sources said.

Prosecutors in the U.S. attorney's office in Maryland then assembled charges and an indictment, using mostly information from the FBI's counterintelligence files and interviews of Campbell done by an Energy Department investigative agent, officials said

Mikerin was an icon in the Russian nuclear industry, a top executive of the state-controlled Rosatom firm and its Tenex subsidiary and the man Moscow sent to Washington in 2010 to oversee Russian President Vladimir Putin's plan to grow uranium sales inside the United States under the Obama administration.

The November 2014 indictment, bearing Rosenstein's name, charged Mikerin with felony conspiracy to interfere with interstate commerce through extortion.

Court documents alleged Mikerin was part of a larger racketeering scheme that also involved bribery, kickbacks and money laundering and that he demanded $50,000 in regular kickbacks from Campbell starting in November 2009 in order for Campbell to keep his consulting work for the Russians.

The court documents portrayed Campbell alternatively as "Victim One" or "Confidential Witness 1" who came forward to report Mikerin's wrongdoing and cooperate with the FBI.

In fact, Campbell had been under the FBI's control informing on the Russian nuclear industry since 2006, had signed a formal nondisclosure agreement with the FBI in 2008 and eventually was rewarded in 2016 with a $51,000 check for his extensive counterintelligence work.

Mikerin eventually pleaded guilty to a money laundering conspiracy charge and was sentenced in December 2015 to 48 months in prison.

A month later, the FBI paid Campbell compensation of more than $51,000, a transaction prosecutors did not learn about until The Hill published a copy of the check last month, officials said.

Congress is now investigating the entire Russian nuclear bribery case after The Hill disclosed Campbell's work, with multiple committees demanding to know whether the FBI told the Obama administration about Mikerin's criminality before the administration made favorable decisions that rewarded Rosatom with billions of dollars in new American nuclear fuel contracts.

Justice officials began briefing congressional officials this week, starting with the Senate Judiciary Committee. After the briefings end, congressional investigators plan to interview Campbell.

After Campbell's name and work surfaced, anonymous allegations surfaced in stories by Yahoo and Reuters suggesting the Justice Department had grave reservations about Campbell's credibility, in part because he had three misdemeanor alcohol arrests.

But officials told The Hill those leaks were not authorized by the Justice Department and did not reflect accurately the official thinking of the department.

For instance, they said prosecutors had no concerns about Campbell's three misdemeanor alcohol arrests and that the FBI held the informant in enough esteem to pay him the check after the case ended. And after prosecutors completed three debriefings with Campbell, they approved the payment in 2015 of the last of his expenses as an undercover.

Prosecutors' concerns primarily dealt with the sequence of events and transactions surrounding Campbell's undercover work during the counterintelligence part of the probe before criminal prosecutors got involved, officials said.