plead
/ˈplēd/
verb
to argue a case or cause in a court of law
to make an allegation in an action or other legal proceeding; especially : to answer the previous pleading of the other party by denying facts therein stated or by alleging new facts
to conduct pleadings
idiomatic phrase
to refuse to testify against oneself in a court of law in accordance with the Fifth Amendment of the U.S. Constitution : take the Fifth —often used figuratively
… appeared … for a deposition, but pled the Fifth dozens of times.
idiom
to say that one knows nothing about something
When asked about the reasons for these drastic changes, she pleaded/pled ignorance.