Original sentence: Clinton’s former State Department chief of staff, Cheryl D.Democratic committee members strongly challenged the significance of Clinton's private email account, saying her use of personal email has been public knowledge for years, and that it follows a pattern of use by previous secretaries of state.Mills, as well as Jake Sullivan, her former deputy chief of staff, each testified at closed meetings of the committee the week of September 1, 2015, and Clinton was scheduled to testify in open session on October 22, 2015.On September 10, 2015, in response to a subpoena to testify before the House Select Committee on Benghazi, Clinton aide Bryan Pagliano, who had maintained her private server while she was Secretary of State, invoked his constitutional Fifth Amendment rights against self-incrimination and declined to answer any questions before the committee