:having made a formal promise to tell the truth in a court of law（在法庭上）宣誓说实话，经宣誓
In a U.S. court of law, a witness must swear under oath to tell “the truth, the whole truth, and nothing but the truth.”在美国的法庭上，证人必须宣誓“说实话，说全部的实话，只说实话”。
He said in testimony given under oath that he was not there the night of the crime.他在法庭上宣誓后做证，案发当晚他不在现场。