House Oversight Committee Chairman Trey Gowdy, R-S.C., does not mind the FBI reopening a background investigation into Supreme Court nominee Brett Kavanaugh to learn more about Christine Blasey Ford's accusation that he sexually assaulted her in high school.

"I have no issues with the FBI taking a second, third, eighth look if that's what it takes to find out what happened and to fully air all the facts," Gowdy said Sunday during an interview on CBS News' "Face the Nation." "I just want people to have realistic expectations."

[More: Democrats escalate calls to delay Kavanaugh hearing, initiate FBI probe]

Gowdy, a former federal prosecutor, said an FBI probe did not mitigate the need for either Kavanaugh or Ford testifying before Congress. The Senate Judiciary Committee should hear from the witnesses to determine their credibility, he stressed, expressing concern over senators claiming they believed Ford, now a professor, without listening to her claim in person.

"So the only role I can see the bureau playing is identifying other witnesses that may have knowledge. Some of that has already been done by Dr. Ford," Gowdy said.

"Judge Kavanaugh's defense is he wasn't there, so you wouldn't expect him to produce witnesses, but I don't know what people expect the FBI to do," he continued. "They're not human polygraphs. They can't tell us who is telling the truth."

Ford alleges Kavanaugh drunkenly forced himself on her during a high school party in the 1980s. They have both agreed in principle to appear before the Senate Judiciary Committee regarding the accusation, but Ford's lawyers and Democrats have argued for an independent inquiry before she faces the panel.