Learn English – saying or idiom for “trying to get the truth from someone by lying”



  • Mary-Ann got home late from school. Asked where she had been, she said she had spent the afternoon at the library. Her father thinks she is lying and says: "I know you haven’t been there because I was there myself". He is lying because he thinks she will tell the truth if she realizes she has been caught.
  • boyfriend – “your sister told me everything” (sister did nothing) –
    girlfriend – “Oh, did she? I’m gonna kill her.

The rationale for doing this is to catch someone by surprise so he will admit having lied. Soemtimes, however, the person isn’t lying and the real liar will have to reap the consequences of his reproachable action, having to admit he was just/it was just ………..(saying or idiom)…..

Best Answer

Sometimes people set a trap in order to force others to make a mistake or own up to the truth. An English idiomatic phrase that fits this type of situation is to trip someone up; if the victim falls (unwittingly) into the trap, then you have successfully caught him/her out.

set a trap (for somebody)
a clever trick that is used to catch someone or to make them do or say something that they did not intend to

catch out
to show that someone has made a mistake or is not telling the truth, especially by asking them questions He asked her casual questions to see if he could catch her out.

Sources: Longman Dict. of Contemporary English, Macmillan Dictionary