The indictment of a former director of the Federal Bureau of Investigation, James Comey, runs to only two pages. That terseness could end up being a liability once the Department of Justice is required to defend it in court. 

Mr. Comey, who led the FBI between 2013 and 2017, when President Trump fired him, is charged with making a false statement to Congress and obstruction of a congressional proceeding. Both of those alleged crimes stem from testimony he delivered in 2020.

The prosecution is being led by the interim United States attorney for the Northern District of Virginia, Lindsey Halligan. She was part of Mr. Trump’s defense team in the Mar-a-Lago documents case and was more recently tasked with reimagining the Smithsonian. She has never prosecuted a felony before. She took over the prestigious post from Erik Siebert, who was also serving on an interim basis. Mr. Trump indicated he fired Mr. Siebert, who was hesitant to charge Mr. Comey, because the prosecutor enjoyed Democratic support.

Mr. Comey could challenge the lawfulness of Ms. Halligan’s appointment. Federal law appears to preclude the appointment of two interim prosecutors in a row. A similar challenge against the top federal prosecutor in New Jersey, Alina Habba, prospered at the district court level, though the ruling disqualifying her is stayed pending appeal from the Department of Justice. 

Ms. Halligan’s signature is on the indictment handed up by the Virginia grand jury, which approved charges on two counts but, unusually, declined to approve a third. For Mr. Comey to be convicted of making a false statement, the government must show that he did so “knowingly and willfully.” Obstruction requires a showing that Mr. Comey acted “corruptly.” 

During the hearing in question in 2020, Mr. Comey told Senator Ted Cruz, “I stand by the testimony you summarized that I gave in May of 2017.” That was a reference to earlier testimony where Mr. Comey told Senator Chuck Grassley that he did not authorize anyone at the FBI to leak information about the investigations into Russian interference in the 2016 election and Secretary Hillary Clinton’s use of a private email server.

Mr. Cruz, though, appeared to be referencing not Mrs. Clinton’s email use but instead a separate investigation, undertaken by the Wall Street Journal, into the Clinton Foundation. The indictment does not specify which investigation is at issue, or what particular leak is being referenced. Even if prosecutors can show that Mr. Comey authorized a leak, the vagueness in the charging instrument means that Mr. Comey could argue that prosecutors failed to nail down which disclosure is being alleged.

Also unclear is whom Mr. Comey authorized to leak. One possibility is his former deputy, Andrew McCabe, who has had his own issues with issuing contradictory statements. In 2019, a grand jury refused to return an indictment for charges relating to the leak to the Journal. Another possibility is a friend of Mr. Comey who is a professor at Columbia Law School, Daniel Richman. Mr. Cruz’s questioning, though, centered on “someone else at the FBI.” It is not clear whether that would comprise Mr. Richman.

The indictment alleges that Mr. Comey “authorized PERSON 3 to serve as an anonymous source in news reports regarding an F.B.I. investigation concerning PERSON 1.” The first reference appears to refer to Mr. McCabe, though Mr. Richman is also a candidate. “Person 1” is likely Mrs. Clinton, though not made explicit is whether the investigation relates to her emails or foundation. The Sixth Amendment requires a defendant to “be informed of the nature and cause of the accusation” against him.

Mr. Trump has benefited from this constitutional requirement. Judge Scott McAfee, a state trial county judge at Fulton County, Georgia, dismissed three charges against the 47th president brought by the district attorney of Fulton County. Those charges related to solicitation of violation of oath by a public officer. Judge McAfee, though, found that they were fatally vague.          

Mr. Comey could also challenge his indictment as selective. Mr. Trump has taken to Truth Social to say: “One of the worst human beings this Country has ever been exposed to is James Comey, the former Corrupt Head of the FBI. … He has been so bad for our Country, for so long, and is now at the beginning of being held responsible for his crimes against our Nation.” He has also declared that “JUSTICE MUST BE SERVED, NOW!!!”

A defendant, though, must clear a high bar to land a claim of selective prosecution. He must prove that others who are similarly situated to them were not prosecuted and that the prosecution was motivated by an impermissible purpose. If that standard is met, the charges are dismissed.