House Judiciary Committee Chairman Bob Goodlatte (R-Va.) denounced Fusion GPS co-founder Glenn Simpson Tuesday for refusing to answer questions as part of a congressional investigation.

“It’s disappointing that Glenn Simpson refused to answer the many questions we have for him as part of our investigation into decisions made and not made by the Justice Department in 2016,” Goodlatte said in a statement provided to LifeZette.

“Mr. Simpson has already voluntarily testified before other congressional committees regarding his firm’s role in compiling the dossier used to obtain a FISA warrant against a U.S. citizen.”

Simpson’s invoking his Fifth Amendment rights was no surprise, since his lawyers warned Monday he would do just that. Goodlatte subpoenaed him to appear before the committee for a deposition as part of a congressional investigation into decisions the Department of Justice (DOJ) made around the time of the presidential election of 2016.

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“The House Judiciary and Oversight Committees sought testimony from Mr. Simpson because he is uniquely qualified to answer questions regarding the dossier collected by Christopher Steele that was then used by the FBI to form an essential part of the Carter Page FISA application,” Goodlatte said.

“We expected Mr. Simpson to answer questions that have not been explored by other congressional committees to help advance our joint investigation. Instead, Mr. Simpson has refused to cooperate with our investigative team and has denied the American people answers to important questions.”

Fusion GPS is the opposition research firm that is a central figure in the growing scandal over the DOJ’s and FBI’s handling of an investigation into allegations that aides to President Donald Trump’s 2016 campaign colluded with Russian interests.

That investigation was, in great part, generated by officials using an unsubstantiated dossier filled with unsavory allegations against Trump that were obtained from Russian intelligence sources by former British spy Christopher Steele.

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Steele was working with Fusion GPS. The dossier was paid for indirectly by Trump’s Democratic opponent, former Secretary of State Hillary Clinton and the Democratic National Committee, which she controlled at the time, through the Washington, D.C., law firm Perkins Coie.

The FBI used the dossier to obtain surveillance warrants from the Foreign Intelligence Surveillance Act court to spy on former Trump campaign aide Carter Page. Fusion GPS hired Steele to compile the dossier, and former Associate Deputy Attorney General Bruce Ohr provided it to the bureau via his wife, Nellie, who worked with Fusion GPS.

Simpson previously testified about the dossier and his involvement at a November 2017 hearing. Ohr later appeared for a closed-door hearing August 28, which some Republicans in the room said implicated Simpson and former FBI lawyer Lisa Page.

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Trump has also been the subject of a special counsel investigation into whether he or his associates colluded with Russian interests during the 2016 election. He and his allies have claimed that the dossier helped lead to that investigation as well.

The House Intelligence Committee reported March 22 that comments former Trump adviser George Papadopoulos made in a London bar to an Australian diplomat set the FBI investigation in motion back in 2016.

Deputy Attorney General Rod Rosenstein later appointed former FBI Director Robert Mueller as a special counsel to take over the investigation.

Congressional investigators also called Rosenstein to testify for a hearing originally set for Thursday. The Hill reported that the hearing had been postponed to an unspecified date. Rep. Jim Jordan (R-Ohio) said Tuesday during an interview on Fox News that Rosenstein should be subpoenaed if he continues to refuse to appear.