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FBI Director James Comey said he started documenting each of his one-on-one conversations with President Trump because he was seriously worried Trump might not tell the truth. "I was honestly concerned that he might lie about the nature of our meeting," Comey said Thursday as he testified before the Senate Intelligence Committee on his conversations with Trump regarding the Russia probe.

Comey also cited concerns about the "circumstances" and the "subject matter." Comey noted that he was alone with Trump and that the topic of their conversations touched on the FBI's "core responsibility" and also related to the president "personally." Comey started taking notes after his first meeting with Trump in January, before Trump had been sworn into office; he also noted that he never felt the need to document his interactions with either former President George W. Bush or former President Barack Obama.

Watch Comey dish on his reasons for taking notes on his talks with Trump below. Becca Stanek