'Start Here': Republicans likely have enough votes to block witnesses in impeachment trial

It's Friday, Jan. 31, 2020. Let's start here.

1. Impeachment trial

A war over witnesses and documents in the Senate impeachment trial could come to an end today with Republicans likely acquiring enough votes to block the measure.

Another vote to acquit President Donald Trump could come as soon as tonight or early Saturday, according to ABC News' Trish Turner on "Start Here."

"There are two votes on the two articles of impeachment that the senators will be standing from their desk voting guilty or not guilty, and that should be the end of it," she says. "As we know, it takes two-thirds to convict and we don't expect Donald Trump to be convicted and removed from office."

2. Brexit time

Three years and two prime ministers after Britain first voted to leave the European Union, Brexit will finally take effect today at 11 p.m. local time.

But it's not quite over yet, says ABC News Foreign Correspondent James Longman in London: "We’re going into a transition period ... nothing actually happens as of Saturday morning ... things will continue as normal until the end of the year.”

3. Scientists and suspected spies

There are growing concerns from federal authorities about China infiltrating elite American biomedical research institutions by recruiting scientists to steal U.S. technology for Beijing's benefit.

This week federal authorities revealed three cases of researchers being accused of hiding their ties to Chinese institutions, including Dr. Charles Lieber, the chairman of the chemistry department at Harvard University.

"Federal prosecutors said they weren't exactly sure all of the research that Dr. Lieber was up to, but they worried that some of it could have military applications," ABC News Senior Investigative Reporter Aaron Katersky tells the podcast. "They also were just wondering why he had fifty thousand dollars a month coming to him from China and what exactly was he giving them?"

Lieber has not yet entered a plea. Harvard officials have placed Lieber on “indefinite” paid administrative leave. The university said in a statement, "Harvard is cooperating with federal authorities, including the National Institutes of Health, and is initiating its own review of the alleged misconduct.”

"Start Here," ABC News' flagship podcast, offers a straightforward look at the day's top stories in 20 minutes. Listen for free every weekday on Apple Podcasts, Google Podcasts, iHeartRadio, Spotify, Stitcher, TuneIn or the ABC News app. Follow @StartHereABC on Twitter, Facebook and Instagram for exclusive content and show updates.

Elsewhere:

'Let me introduce myself': A former congressman allegedly linked to Rudy Giuliani’s shadow campaign to oust America’s then-ambassador to Ukraine appears on video, obtained by ABC News, meeting with President Donald Trump.

'A simple saliva sample': E. Jean Carroll, the writer who's claimed Trump sexually assaulted her in a Bergdorf Goodman dressing room in the 1990s, asked on Thursday for a DNA sample from the president to compare to the genetic material she says is on a dress she wore at the time of the alleged assault.

'Lip service is not enough': Brian Hook, the U.S. special representative for Iran, said Thursday that the Iranian regime had diverted humanitarian money and goods to its elite members.

From our friends at FiveThirtyEight:

FiveThirtyEight's Nate Silver says that although the Iowa caucuses are only four days away, almost anything could still happen.

Doff your cap:

Deandre Arnold, a senior at Barbers Hill High School in Mont Belvieu, Texas, faced in-school suspension and possibly being banned from his graduation walk ceremony because the length of his dreadlocks violates the school's policy.

The teen's story landed him on "The Ellen Show" Wednesday -- where the aspiring veterinarian got a huge surprise when singer Alicia Keys appeared onstage and presented him a $20,000 check from Shutterfly to be applied toward his college education.

"You're a special person and you're destined for such greatness," the singer told him.