ANALYSIS | Everything you need to know about the January 6 federal investigation

Is there enough evidence to try Donald Trump?

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(CNN) --

By now, everyone is at least aware that a House select committee is investigating the January 6 riots at the US Capitol.

Through its public hearings, this commission has attracted much attention.

Of lower profile is the ongoing Department of Justice (DOJ) investigation into the insurgency.

That investigation has already led to more than 800 arrests of those who participated in the riot and has also increased pressure on major players in Trump's world, such as attorney John Eastman and former Justice Department official Jeffrey Clark.

• 'This is a bombshell': Trump aides gasped at Hutchinson's testimony

To help better understand what the DOJ is doing, I reached out to Katelyn Polantz, who covers crime and justice for CNN.

Our conversation, done over email and lightly edited for flow, is below.

Cillizza: Let's start with something simple: when did the federal investigation start around January 6 and what do we know about it?

Polantz

- A Simple Answer to a Simple Question - Started on the evening of January 6, 2021.

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That's when the obvious crime took place: hundreds of Trump supporters looting the Capitol.

That very quickly got the full attention of the Justice Department.

We saw the first federal arrests—including that of QAnon shaman Jacob Chansley—within days of the attack, and more than 800 people have been charged over the riots.

The group includes members of the Proud Boys and Oath Keepers, who are facing charges of seditious conspiracy.

At the end of the first year, Attorney General Merrick Garland made it clear that the Justice Department would continue its investigation, studying the money and the communications, and following where the evidence led.

That's when we began to learn that people who were not on Capitol grounds, but in political circles, were part of this investigation.

This represented a clear expansion of grand jury activity looking into Trump's staging of rallies and false electors in battleground states.

There is investigative activity that is still in its early stages, with no apparent charges arising from it yet.

But the DOJ is getting more aggressive every week.

In the past week alone there have been dozens of new subpoenas, in addition to the records of John Eastman and Jeffrey Clark.

We don't know where this is taking us yet, but the amount of information that is being collected already goes a long way in the communications field of the Trump field.

Hutchinson: Trump approved of chants calling for Pence to be hanged 2:57

Cillizza: How, if at all, are you coordinating this investigation with the House committee?

Does one influence the other or not?

Polantz

: Nothing happens in isolation in Washington.

The House Select Committee is doing an unusually good job of working quickly and digging deeply on their own, especially given how much they have been able to gather through witness interviews (over 1,000), records from the National Archives and Eastman's emails.

That accumulation of evidence will end up in the public domain.

The Justice Department has also been working through mountains of mind-boggling evidence, especially in preparation for trials.

The House of Representatives has focused on the top of the pyramid — Trump himself — while the Justice Department traditionally investigates from the bottom up, starting with the troublemakers themselves.

We're starting to see those interests intersect now that the DOJ wants access to transcripts of witnesses who have spoken to the House and can't do so as easily as investigators want.

The House of Representatives says that it will eventually publish all of its material.

But the wall between the work of Congress and the DOJ at this point has become a point of tension.

Cillizza: The debate in the January 6 commission is whether to recommend criminal charges be filed in its final report.

Does that decision have anything to do with this federal investigation?

Polantz

: Probably not.

A lot of ink has been spilled on whether or not committee members will make a referral.

Some members of Congress have a rich history of trying to tell the Justice Department who to investigate, to little avail.

Now, as then, the Justice Department doesn't need Congress to expose violations of the law, it has its own nose (and stronger search and subpoena power).

For example: The DOJ search of Clark came the day before his former colleagues gave scathing testimony about his actions at the end of the Trump administration to the House committee.

Still, Garland has made it clear that his department is watching these commission hearings.

If something comes to the attention of investigators that is revealed on Capitol Hill, it's entirely possible they'll move faster than it might take to write a final report or referral.

Cillizza: The FBI has subpoenaed, among others, the chairman of the Georgia Republican Party.

Is the research looking at all the oscillating states?

Or do we not know?

Polantz

: We do know that the bogus voter investigation has canvassed information from all seven states where Trump voters rallied.

But he remembers: the subpoenas we know about in this investigation are not just looking for details about political actors at the state level.

They are also asking for the communications those people had with some of the higher levels of the Trump campaign, with everyone from Rudy Giuliani to Eastman to Boris Epshteyn.

Cillizza: Finish this sentence: "The danger to Donald Trump from this investigation is _______________."

And explain it.

Polantz

: "Who may be willing to share what they have witnessed."

Perhaps Trump is in no danger and has never crossed the line of the law.

This cannot be known until the facts are gathered.

• Who is Cassidy Hutchinson, the Meadows aide who offered explosive testimony before Congress?

The facts are already coming to light on live television.

Cassidy Hutchinson has outshone other witnesses as the star of the House investigation.

But don't forget that every House public hearing has drawn startlingly candid testimony from various Trump administration officials — including former Attorney General Bill Barr;

Eric Herschmann, a lawyer who worked in the Trump White House;

Richard Donoghue, former Acting Deputy Attorney General;

and Greg Jacob, who was an adviser to Mike Pence when he was vice president—often about his deep disagreement with the president and how he or others close to him were warned of the wrongness of their beliefs about the 2020 election.

Hutchinson reiterates testimony about Trump's conduct 0:44

Trump was unable to maintain a firewall in the Robert Mueller investigation, and key people like White House counsel Don McGahn became witnesses against him in the obstruction investigation.

But some of his advisers chose to endure trial — and they will go to their graves — without revealing the full truth of what happened inside the Trump campaign when Russia hacked the Democrats.

January 6 is different, even a former Trump defense attorney has told me.

In the last week at least, transparency is gaining momentum.