Dr. Anthony Fauci declined to answer senators’ questions at a hearing Wednesday on the origins of Covid and the government’s handling of the pandemic, saying in prepared remarks that he would invoke his 5th Amendment right not to testify to avoid the possibility that Republicans could try to use his testimony to prosecute him for perjury.

The surprise decision shook up the hearing, which was expected to be contentious given Fauci’s previous public clashes with Chairman Rand Paul, R-Ky.

In his opening statement to the Senate Homeland Security Committee, Fauci pointed to Paul’s “obvious obsession with calling for my prosecution, his repeated slanderous comments about me” and his decision to publicly release the doctor’s personal journal.

“The only conclusion I can reach is that the sole reason he is calling me before this committee is to get me to say something that could vindicate his repeated public pledges that I end up, in his words, ‘behind bars,’” Fauci said.

“Any reasonable person who has followed his unhinged obsession with me would readily come to the same conclusion,” he continued. “Therefore, although it pains me to do so because of the respect that I have for the legislative branch of government and my decades long record of cooperating with Congress, under the advice of my attorneys, I will invoke my right under the 5th Amendment of the Constitution to refrain from answering your questions.”

Ahead of the hearing, Paul pointed to the possibility of Fauci facing prosecution for perjury if he lied to Congress. Paul has previously alleged that Fauci has lied to Congress, an allegation that Fauci has denied.

On Tuesday, Paul responded to a reporter’s question about how he would respond to people who argue that the senator was trying to put Fauci in a position to perjure himself.

“There’s no risk to perjury if you tell the truth,” Paul said. “In fact, he can even admit to not telling the truth in the past. He can admit destroying records. He can admit to, you know not adequately presenting both sides of equations, which isn’t really a crime. He can admit to anything. The only thing he can’t do is lie again.”

Former President Joe Biden issued a preemptive pardon for Fauci in the final hours of his administration. Fauci responded at the time by saying that he had been “the subject of politically motivated threats of investigation and prosecution.” The doctor said he “committed no crime.”

Responding to a question earlier this week about whether he believed Fauci should face prosecution, Paul said, “I think there are a couple of questions,” adding that “we’re going to find out” at the hearing. Paul referenced Fauci’s pardon and expressed the possibility that it could be challenged.

“Whether that will be challenged, I don’t know,” Paul said.