Former FBI Director James Comey wrote in his upcoming book that the attorney general under President-elect Joe Biden's administration should not investigate President Trump for a possible criminal case, even if there may be evidence.

In excerpts of "Saving Justice: Truth, Transparency and Trust," obtained and reported by The Guardian, Comey claimed that restoring the public's confidence is of greater importance than prosecuting Trump.

Biden is expected to pick Judge Merrick Garland for attorney general, three Democratic sources confirmed to Fox News Wednesday.

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"Although those cases might be righteous in a vacuum," Comey writes, "the mission of the next attorney general must be fostering the trust of the American people."

Comey couched his statement in language that reflected a belief that there are ample grounds to charge Trump if a prosecutor would be so inclined. He said that the next attorney general should not pursue matters regardless of "how compelling the roadmap left" by Robert Mueller or "how powerful the evidence strewn across his history of porn stars and financial fraud."

Comey was referencing special counsel Mueller's report following the Russia probe that discussed Trump's actions "that raised questions about whether he had obstructed justice" without reaching any conclusions about whether the president was guilty of any crimes. He also appeared to allude to payments made to adult film star Stormy Daniels and model Karen McDougal, for which former Trump attorney Michael Cohen pleaded guilty to campaign finance violations. Cohen has said that he arranged for those payments at Trump's direction.

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Mueller assumed the role of special counsel, leading the Russia investigation that had been launched by Comey's FBI after Trump fired Comey in May 2017. Following his departure, a friend of Comey's who teaches at Columbia Law School leaked information from documents Comey wrote memorializing conversations he had with Trump.

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Comey later admitted to the Senate Intelligence Committee that he asked his friend to leak the memos "because I thought that might prompt the appointment of a special counsel."