The phone call, according to Trump critics, had the president leveraging his power to hold nearly $400 million in aid to Ukraine in exchange for information on the Bidens. Trump says the call congratulating Volodymyr Zelensky on becoming president of Ukraine was “perfect” and has been misinterpreted.
Trump claims that Hunter Biden profited from an affiliation with a Ukrainian gas company and that Joe Biden had a prosecutor who was looking into the operations of the gas company fired to protect his son. Neither Biden has been officially accused of wrongdoing.
The inquiry moved into a public phase last week with the testimony of George Kent, a deputy secretary of state, William Taylor, charge d'affaires to the Ukraine and Marie Yovanovitch, former ambassador to Ukraine.
Here is the list of the eight people scheduled to testify this week:
Tuesday at 9 a.m. ET
Lt. Col. Alexander Vindman: Vindman is the National Security Council's specialist on Ukraine. Vindman listened in on the July 25 call between Trump and Zelensky. He reported concerns about the call to John Eisenberg, the top NSC attorney. According to Vindman, it was Eisenberg who decided to move the record of the call to a classified system.
Jennifer Williams: Williams is a foreign service aide who worked in Vice President Mike Pence's office. She also listened to the call.
Tuesday, 2:30 p.m. ET
Kurt Volker: Volker is the former special envoy to Ukraine. He is one of the people who Republicans had requested to be called as a witness. Volker, along with Gordon Sondland and Secretary of Energy Rick Perry, makes up the "three amigos" who Trump asked to take care of Ukraine policy.
Tim Morrison: Morrison is also on the Republicans' list of requested witnesses. He listened to the July 25 call but has testified in a private deposition that he did not find the call inappropriate and that there was nothing illegal in the request.
Wednesday at 9 a.m. ET
Gordon Sondland: Sondland is Trump's ambassador to the European Union. In his initial testimony before the Intelligence Committee, Sondland said he did not believe that Trump tied military aid to Ukraine to an investigation of Joe Biden and his son Hunter. He has since changed his testimony, saying he "presumed" that the suspension of military aid to Ukraine was linked to the Ukrainian government announcing investigations into the Bidens. Sondland said he personally told an aide to Zelensky that the release of military assistance to Ukraine would only happen if the investigations were undertaken.
Wednesday at 2:30 p.m. ET
Laura Cooper: Cooper, who is a deputy assistant secretary at the Defense Department, testified in closed-door testimony that Ukrainian officials contacted the DoD about the delay in military aid. Cooper brought the matter to Volker and was told, she testified, that he said he was working with Ukrainian officials to make a statement that disavowed election interference.
David Hale: Hale is the State Department's undersecretary of state for political affairs. He was on the list of witnesses Republicans asked to be called to testify publicly.
Thursday at 9 a.m. ET
Fiona Hill: Hill is the top Russia adviser on the NSC. She testified that she raised concerns about a parallel foreign policy channel that Trump's personal attorney, Rudy Giuliani, was using to deal with issues in Ukraine. She took her complaints about Giuliani to John Bolton, who was the national security adviser at the time. Bolton described Giuliani as "a hand grenade that is going to blow everybody up."