Regarding federal investigations, most folks that are interviewed / interrogated are not formally placed under oath. Rather, the interviewee is reminded that this interview is being performed as part of a federal investigation, and that is it a punishable offense to knowingly lie, mislead, providing false information, etc. as part of the interview process within the investigation.
Remember this federal statute: 18 USC 1001.
This code section states:
whoever, in any matter within the jurisdiction of the executive, legislative or judicial branch of the United States, knowingly and willfully (1) falsifies, conceals, or covers up by any trick, scheme or device a material fact; (2) makes any materially false, fictitious, or fraudulent statement or representation; or (3) makes or uses any false writing or document knowing the same to contain any materially false, fictitious, or fraudulent statement or entry; shall be fined under the this title, imprisoned not more than 5 years.
It is a bear and it has extra long teeth and claws.
Many folks falsely remember that Martha Stewart was convicted of securities fraud, that Scooter Libby was (wrongly) convicted of "outing" former CIA agent Valerie Plame, and that Rod Blagojevich was convicted of selling a US congressional seat. In fact, each was predominantly convicted as violating 18 USC 1001 for "lying" to federal investigators during their interviews while under investigation.
Mrs. Clinton provided materially false and fraudulent statements and representations before the legislative branch during its investigation of the Benghazi incident. Each instance of providing materially false/fraudulent statements is punishable by fine and by 5 years of prison. Each. Instance.
Although Dir. Comey's damning statements on Tuesday concluded in a recommendation of pressing no charges, his statements on Tuesday and his testimony today provide all the ammunition necessary to indict Mrs. Clinton on multiple counts of violating 18 USC 1001. It only requires a federal prosecutor with the courage (and possible excellent connection to high-grade security) to file such charges.