ALEXANDRIA, Va. —

The prosecution of former FBI Director James Comey hit another hurdle Wednesday as the Justice Department acknowledged a possible lapse in how the case was presented to a federal grand jury for indictment.

The concession risked further imperiling a politically charged prosecution already subject to multiple challenges and demands for its dismissal. It came during a hearing in which Comey's lawyers asked U.S. District Judge Michael Nachmanoff to throw out the case on grounds that the government was being vindictive. A separate challenge to Lindsey Halligan, the hastily appointed and inexperienced prosecutor who secured the indictment, is pending.

The revelation that the full grand jury did not review a copy of the final indictment in the case is the latest indication of

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