So, now I am Chris Cuomo and welcome to Prime Time.

We're just getting some breaking news on the impeachment inquiry.

A first-hand witness to the president's phone call on Ukraine is due to testify tomorrow.

Brand new reporting. This man may solidify what should be an obvious point.

What do you say? Let's get after it.

This is CNN Breaking News.

All right, so now we're expecting a new testimony tomorrow.

We're just getting this information in.

We are trying to understand what it will mean for us, but look,

a White House national security official.

All right, the main Ukraine expert.

He is called the top expert here by the New York Times.

Lieutenant Colonel Alexander Vinman of the Army.

Why does he matter?

Well, expertise understands Ukraine,

national security, US policy is his domain.

He heard the phone call in July, okay?

No hearsay, not some political pawn, an expert, a military man on the call.

He was very concerned by what he heard and believes that it was out of an act of sense of

duty that he not once but twice registered complaints.

Now, the key question becomes about what?

Here it is.

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