Originally posted by the Voice of America. Voice of America content is produced by the Voice of America, a United States federal government-sponsored entity, and is in the public domain. 3 Witnesses Kick Off First Week of Historic Impeachment Hearings Masood Farivar CAPITOL HILL - The U.S. House of Representatives holds its first public hearings this week on the impeachment inquiry into President Donald Trump with testimony by three top diplomats on Wednesday and Friday. William Taylor, the highest-ranking U.S. diplomat in Ukraine, and George Kent, a senior State Department official in charge of U.S. policy toward Ukraine, are set to testify on Wednesday, followed by Marie Yovanovitch, the ousted former U.S. ambassador to Ukraine, on Friday. All three diplomats have previously testified behind closed doors about Trump's efforts to pressure Ukraine to investigate former Vice President Joe Biden, and probe a discredited conspiracy theory regarding the 2016 president election. Democrats say the open hearings will allow the public to assess the credibility of the witnesses and their testimonies. Republicans are likely to attempt to discredit the impeachment proceedings and poke holes in the witnesses' testimony. Here is what you need to know about the three witnesses and their role in the Ukraine affair. .