Prosecutors deemed GOP's key witness in Hillary-Uranium One probe too 'unreliable' to use in court: report

A key witness in the Republican Party's probe of Hillary Clinton's involvement in the sale of mining company Uranium One to Russian firm Rosatom was once reportedly deemed too "unreliable" to serve as a witness in a separate case involving Russian money laundering.

Sources tell Yahoo News' Mike Isikoff that prosecutors removed former FBI informant William Douglas Campbell as a witness in a case against Russian businessman Vadim Mikerin because he made claims against Mikerin that he could not sufficiently back up with evidence.

"He proved a 'disaster' as a potential witness in the case when doubts arose about his descriptions of some events that could not be documented," Isikoff writes. "As a result, prosecutors dropped extortion charges against Mikerin that relied on Campbell’s testimony."

Although Mikerin eventually pled guilty to some money laundering charges, they had no connection with the testimony given by Campbell.

Campbell's attorney, Victoria Toensing, called the accusations against her client a "smear job" and said the Obama administration ordered that prosecutors throw out extortion charges against Mikerin because it would have endangered the Uranium One sale.

Campbell in the past has suggested that he has the goods to prove that the Uranium One sale was a quid pro quo that aimed to benefit Clinton Foundation donors.