By Eric Lichtblau
A former aide to Hillary Clinton when she was secretary of state testified behind closed doors for two hours Wednesday in the first in a series of depositions that are likely to raise more questions about Mrs. Clinton’s use of a private email server just as she prepares for an election campaign against Donald J. Trump.
The former aide, Lewis A. Lukens, testified under oath about his knowledge of Mrs. Clinton’s private email system as part of a lawsuit brought against the State Department by a conservative legal advocacy group, Judicial Watch.
At least five other officials — including two of Mrs. Clinton’s top aides at the State Department, Cheryl Mills and Huma Abedin — are also scheduled to testify in the lawsuit over the next six weeks in what promises to be an unwelcome distraction for the Clinton campaign.
The last deposition is set for June 29 — less than a month before the start of the Democratic National Convention in Philadelphia, where Mrs. Clinton is widely expected to win her party’s nomination for president over challenger Bernie Sanders.
Meanwhile, the F.B.I. is continuing to investigate the issue of Mrs. Clinton’s private email server to determine whether any federal laws regarding the handling of classified material or other issues may have been broken.
James Comey, the F.B.I. director, told reporters last week that he would not let the campaign calendar dictate the schedule for his agency’s investigation. The Justice Department will ultimately make any decision on charges.
The F.B.I. has already interviewed both Ms. Abedin and Ms. Mills, and it is also expected to speak with another former aide, Jake Sullivan, officials said.
Mrs. Clinton herself has offered to sit down with the F.B.I. in the email case, and that interview – which is sure to generate enormous political and legal attention — could come in a matter of weeks.
Judicial Watch sued the State Department under the Freedom of Information Act for records relating to Ms. Abedin’s special employment status at the State Department under Mrs. Clinton, who was also a close friend. The legal affairs group has been a frequent antagonist of both Hillary and Bill Clinton over the years.
After The New York Times reported last year that Mrs. Clinton had used a private email account exclusively during her entire tenure at the State Department, a federal judge in the lawsuit allowed Judicial Watch to conduct discovery and gather evidence about how the private email server was created at the State Department.
The judge, Emmet G. Sullivan of United States District Court in Washington, has been sharply critical of the State Department’s handling of the email affair over the last year.
“It just boggles the mind that the State Department allowed this circumstance to arise in the first place,” said Judge Sullivan, who was appointed to the Federal District Court in 1994 by President Clinton.
The judge called the email episode “very, very, very troubling.”
Mr. Lukens, a former ambassador to Senegal, was the leadoff witness in the Judicial Watch depositions. He served as executive director of the State Department’s executive secretariat under Mrs. Clinton until 2011, providing her with logistical, administrative and travel support. Judicial Watch said it was seeking his testimony because records that have already been released indicated that he had emailed Ms. Mills and others about Mrs. Clinton’s private email server.
Thomas Fitton, the president of Judicial Watch, who took part in Mr. Lukens’s deposition, said afterward that he could not discuss the substance of the testimony because of the ground rules set by Judge Sullivan.
But Mr. Fitton predicted that once the testimony is publicly released — perhaps as early as next week — it would show “why the State Department and Mrs. Clinton have slow-rolled this and withheld a complete explanation of what went on with her email system. What we learned is going to be embarrassing to Mrs. Clinton and the administration — maybe more than embarrassing.”
He refused to elaborate, citing the court’s restrictions.
After the deposition, State Department lawyers invoked a procedure to review Mr. Lukens’s testimony for three days before deciding whether to ask the judge to keep any parts of it confidential for security or legal reasons.
The State Department declined to comment on the deposition.
“As is standard, the State Department does not comment on matters in litigation,” a department spokesman said.
The Clinton campaign had no immediate comment on the deposition, and Mr. Lukens could not be reached for comment.