Acting U.S. Ambassador to Ukraine Bill Taylor will return to Washington, D.C. for a deposition on Oct. 22 as part of the investigation into President Trump's reported misconduct involving Ukraine.

Why it matters: As the White House maintains a stance of blanket noncooperation, some officials are defiantly providing testimony to Congress. A collection of text messages released last week revealed Taylor was troubled by his impression that $400 million in military aid to Ukraine was used as leverage. Taylor also reportedly witnessed Trump's efforts to press the Ukrainian president for an investigation into Joe Biden's son, NBC News notes.

Go deeper: What matters most in the Trump-Ukraine scandal