FBI director James Comey told the House Judiciary Committee on Wednesday that he could not remember why the agency determined that former Cheryl Mills did not know about Hillary Clinton’s private email server, when there was proof she did.

Mills, former Secretary of State Hillary Clinton’s chief of staff at the State Department, and now her lawyer, wrote personally to Clinton’s private staff about the server, but then told the FBI she did not even know what a “server” was. As the Wall Street Journal‘s Kimberly Strassel notes in a column on Friday, the deception ought to have earned Mills a prosecution for perjury — and a deeper probe of Hillary Clinton — but the FBI chose to look the other way.

Not only did Mills receive immunity from the Department of Justice, but she was also allowed to sit in on the FBI’s interview with Clinton — and to walk out of her own interview with the FBI when she was asked questions about the email scandal that she decided she did not have to answer.

Central to Mills’s apparent super-immunity is her assertion of attorney-client privilege. The privilege, which can only be waived by the client, prevents an attorney from disclosing any communications from his or her client. Mills asserted that she did not have to tell the FBI about the server because she only learned about it once she was Clinton’s attorney — i.e. after she left the State Department, where she had been a “counselor” and chief of staff but did not represent Clinton personally.

The only way to square these contradictory facts is to believe the incredibly unlikely theory that Mills knew about the server when she was at the State Department, but forgot about it when she left, then was reminded about it by Clinton once she was her attorney, but could not talk about it without permission from Clinton at that stage, thanks to the attorney-client privilege she conveniently enjoyed.

It is not the first time Mills has been linked to a cover-up. In 2013, a State Department diplomat who had been in Libya during the Benghazi attacks told Congress that Mills had instructed witnesses not to cooperate with Congress. She is also alleged to have interfered with other investigations.

Joel B. Pollak is Senior Editor-at-Large at Breitbart News. His new book, See No Evil: 19 Hard Truths the Left Can’t Handle, is available from Regnery through Amazon. Follow him on Twitter at @joelpollak.