JUDY WOODRUFF: The Russia probe ramps up.

Late today, The Wall Street Journal is reporting that special counsel Robert Mueller is using a grand jury in Washington, D.C., marking a new phase in the investigation into Russian interference in the 2016 election.

Joining me now to walk us this could mean is Steve Bunnell. He is the former chief of the Criminal Division at the U.S. Attorney's Office here in Washington.

Steve Bunnell, welcome to the program. First of all, explain to us, remind us of is a grand jury, what does it do?

STEVE BUNNELL, Former Federal Prosecutor: Well, thank you, Judy, for having me.

A grand jury is 23 citizens who sit to review proposed charges and vote indictments. And in the federal system, they typically are involved in long-term investigations as well.

JUDY WOODRUFF: So, what is it — I mean, we don't have all the information here, but based on what we know, what is the significance of this news?

STEVE BUNNELL: Well, it appears that the investigation is getting more intensified, it's getting more serious.

It could be a consolidation of grand jury investigations which have been reported in other districts, but certainly a grand jury is used for collecting financial information and for doing long-term, deep-dive investigations.

JUDY WOODRUFF: There had been reports that Robert Mueller was using a grand jury in Virginia, perhaps using one in New York City. What would this new grand jury permit him to do that he couldn't do before?

STEVE BUNNELL: It wouldn't expand the authorities that he has. It may be a little more convenient for him, if he doesn't have to travel so far to actually present evidence or to present witnesses. So, it doesn't expand his ability to collect evidence. It may just make it more convenient.

JUDY WOODRUFF: Does it say anything about the seriousness of what he is doing?

STEVE BUNNELL: Well, it suggests that the investigation is not ramping down. It suggests that it is at an early stage of ramping up.

And the fact that there is a new prosecutor that recently joined the team that we have learned about, that suggests that this investigation will be a serious, intensive investigation that will go on for some time.

JUDY WOODRUFF: There — again, there have been reports that Mr. Mueller is not only looking at, of course, the Russian activity, but he is looking at financial transactions, possibly financial transactions on the part of President Trump. Can one read anything along those lines into this?

STEVE BUNNELL: Well, Bob Mueller is a very experienced prosecutor and law enforcement individual.

And he knows that you investigate potential crimes. You don't investigate people. And so I think what he's doing is investigating a set of allegations, a set of potential crimes. And whatever individuals may be involved in that will be sort of part of that investigation.

JUDY WOODRUFF: How does something like this get out into the public realm? It is supposed to be secret, am I right? So how does it — what happens?

STEVE BUNNELL: Well, the federal rules of criminal procedure impose secrecy obligations on the prosecutors, on the grand jurors themselves, on the agents that work with the prosecutors.

But the witnesses who appear before a grand jury or people who receive subpoenas are free to talk about what — you know, what the grand jury ha asked them. And so it's not uncommon for grand jury investigations to get out into the public domain through witnesses or people who receive subpoenas.

JUDY WOODRUFF: And final question, what does this say about how long this could take? I mean, are we looking at weeks, months, longer?

STEVE BUNNELL: I would say longer, certainly not weeks. I would guess several, many months.

Federal grand juries are impaneled for 18 months and can be extended another six months. And financial investigations take a long time, especially if you are trying to obtain records from overseas locations.

JUDY WOODRUFF: Steve Bunnell, attorney here in Washington, former prosecutor, thank you very much.

STEVE BUNNELL: Thank you very much.

JUDY WOODRUFF: All this as two separate pieces of bipartisan legislation emerged in the U.S. Senate designed to protect special counsel Mueller if President Trump were to decide to fire him.