According to a Wall Street Journal article on Aug 3, Special Counsel Robert Mueller has impaneled a grand jury in Washington to investigate Russia’s interference in the 2016 elections. Several news organizations have also reported that in recent weeks Mueller has been issuing subpoenas through federal grand juries in D.C. and Virginia to both evaluate and add to the evidence investigators have obtained about the Trump team’s ties to Russia. In this Q&A, Stanford Law School Professor David Alan Sklansky breaks down the grand jury process and explains what Mueller and his team are doing.

What is the purpose of a grand jury?

In theory, grand juries have two roles:  they decide, in felony cases, whether there is enough evidence for someone to be charged, and they issue subpoenas for documents and for testimony.  In practice, though, grand juries almost always follow prosecutors’ recommendations about whether to issue an indictment, so the real importance of grand juries is as an investigative tool for prosecutors.

Is this the normal course of things for a special investigation—or is the use of grand juries a sign that his inquiry is growing?

It is absolutely the normal course of things for any complex criminal investigation in the federal system.  What would be surprising is if Mueller decided not to use a grand jury.

Why is it necessary for Special Counsel Mueller to issue subpoenas for his investigation through a grand jury?

Prosecutors don’t have subpoena power.  Courts do, and a grand jury is, technically, an arm of a federal district court.

What’s the significance of the report that, in addition to using existing grand juries in D.C. and Virginia, Mueller has impaneled a new grand jury in Washington?

Hard to say for sure, because Mueller is conducting his investigation confidentially, as he should.  But a grand jury ordinarily can only issue indictments for crimes that occurred in the district where the grand jury sits, and it only has jurisdiction to investigate crimes for which it could issue indictments.  So, if Mueller is investigating crimes that he has reason to suspect took place in DC, it would be appropriate for him to use a grand jury in DC.  He could use an existing grand jury in DC, but in a complex investigation it is common to want to start with a newly impaneled grand jury.  Grand jurors typically serve for fixed terms, and although their appointments can be renewed, you don’t want to do that if you can avoid it, and if you can’t avoid it, you don’t want to have to do it repeatedly.  And in a large, complex investigation run out of an independent office—like Mueller’s investigation—it makes sense, just in terms of administrative convenience, to have a separate grand jury instead of having to coordinate with prosecutors using the grand jury in other investigations.

Is this a criminal investigation?

It’s definitely a criminal investigation.  It was a criminal investigation from the outset.  That was what Mueller was appointed to conduct.  And you can’t use a federal grand jury if there’s no criminal investigation.

What do you expect as the next steps for Mueller?

Collecting and analyzing documents, interviewing witnesses, and having witnesses testify before the grand jury—the normal step-by-step of a complex federal criminal investigation.

David Alan Sklansky, a former federal prosecutor, is the Stanley Morrison Professor of Law at Stanford Law School. He is also a faculty co-director of the Stanford Criminal Justice Center (SCJC).