The National Archives and Records Administration(NARA) found in 2021 that Trump had taken presidential documents with him to his home in Florida after leaving office. After Trump returned some documents, NARA found others were still missing, including some that were highly classified. NARA referred the matter to the FBI, and after requests and a subpoena to return the documents went unheeded, the FBI entered Trump’s home under a search warrant to retrieve them. Patel publicly asserted that Trump had declassified broad sets of sensitive documents before leaving the White House. In October 2022, Patel was summoned to testify before a federal grand jury investigating the matter, but he declined to answer questions by invoking his Fifth Amendment right against self-incrimination. Patel was represented in the matter by lawyer Stanley Woodward.[43] The Justice Department sought unsuccessfully to persuade a federal judge to compel Patel’s testimony, whereupon he was granted immunity to testify, which he did on November 4, 2022.

https://en.m.wikipedia.org/wiki/Kash_Patel#Involvement_in_Trump_documents_investigation