Roger J. Stone Jr., a longtime adviser to President Trump, is the sixth Trump adviser or official to be charged in the special counsel investigation. Robert S. Mueller III, the special counsel investigating possible links between the Trump campaign and Russian officials, has issued more than 100 criminal counts against dozens of people and three companies.

Several others have been charged in investigations that stemmed from Mr. Mueller’s inquiry, as well as a broader counterintelligence investigation by the Justice Department and the F.B.I.