on/under oath

on oath

Bound by a formal promise to tell the complete and honest truth about an event while on the witness stand in a trial. You are on oath as a witness in this trial, so you must answer my questions completely truthfully! Consider your answer carefully—you're still on oath.
See also: oath, on

under oath

Bound by a formal promise to tell the complete and honest truth about an event while on the witness stand in a trial. You are under oath as a witness in this trial, so you must answer my questions completely truthfully! Consider your answer carefully—you're still under oath.
See also: oath
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.

under oath

Fig. bound by an oath; having taken an oath. You must tell the truth because you are under oath. I was placed under oath before I could testify in the trial.
See also: oath
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs. © 2002 by The McGraw-Hill Companies, Inc.

on/under ˈoath

(law) having made a formal promise to tell the truth in a court of law: Is she prepared to give evidence on oath?The judge reminded the witness that he was still under oath.
See also: oath, on
Farlex Partner Idioms Dictionary © Farlex 2017

under oath

Under a burden or responsibility to speak truthfully or perform an action faithfully.
See also: oath
American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
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