4,500 tips to FBI went uninvestigated following supplemental investigation, newly released FBI letter shows Thank you for the FBI’s June 30, 2021 response to our August 1, 2019 letter regarding the supplemental background investigation of then-Judge Brett M. Kavanaugh. Your letter confirms that the FBI’s tip line was a departure from past practice and that the FBI was politically constrained by the Trump White House. It also belies the former president’s insistence that his administration did not limit the Bureau’s investigation of Justice Kavanaugh, and his claim that he “want[ed] the FBI to interview whoever [sic] they deem appropriate, at their discretion.”