As the other comment pointed out, they have a set of very particular facts and will press you with questions about dates, times, amounts, who, what, where, and when. If you say a not true statement about one of those things they charge you with lying. The relevant law is 18 U.S. CODE § 1001. It's 3 pronged and the 2nd says "makes any materially false, fictitious, or fraudulent statement or representation; or". I don't believe there is a requirement in this law for criminal intent, caveat IANAL.