During an interview on MSNBC, Booker said that he chose to testify against Sessions because the Alabama senator has voted or spoken out against "key ideals around the Voting Rights Act" and taken steps "to block criminal justice reform."
"He has a posture and a positioning that I think represent a real danger to our country," Booker said.
Civil rights icon Rep. John Lewis (D-GA) and Rep. Cedric Richmond (D-LA) will also testify against Sessions, according to the Senate Judiciary Committee's schedule for the hearing.
The three black lawmakers will testify on the third and final panel of the hearing, a move that upset Democratic lawmakers. Democrats argued that it is customary for sitting lawmakers to testify before outside witnesses are called. But Sen. Chuck Grassley (R-IA), the chair of the Judiciary Committee, refused to let the lawmakers testify ahead of outside witnesses who had already been called to speak before the committee.