1
general::
Phrase(s): How should I know? [and] Don’t ask me.
Inf. I do not know.; Why should I be expected to know? (Shows impatience or rudeness.) • Bill: Why is the orca called the killer whale? Mary: How should I know? • Sally: Where did I leave my glasses? Tom: Don’t ask me.
McGrawhill's American Idioms And Phrasal Verbs