JM 1-6.630
When appearing in an official capacity on behalf of the United States, Department of Justice employees are serving on official duty, without charge to leave. An employee who is summoned as a witness in a judicial proceeding in which the Federal, State, or local government is a party is entitled to court leave, without charge to personal leave. See 5 U.S.C. § 6322. Employees are not entitled to official time or leave to appear voluntarily as a witness for a private party.
[updated April 2018]