Donald J. Trump has long derided public figures who invoke their constitutional right against self incrimination, but on Wednesday he took full advantage of the Fifth Amendment.

For hours under oath, Mr. Trump sat across from the New York State attorney general, Letitia James, responding to every question posed by her investigators by repeating the phrase “same answer” over and over again.

Mr. Trump’s refusal to respond substantively to any questions in the court-ordered deposition was an unexpected twist that could determine the course of Ms. James’s three-year civil investigation into whether the former president fraudulently inflated the value of his assets to secure loans and other benefits.

It was also an extraordinary moment in an extraordinary week, even by the former president’s standards. Two days after his home was searched by the F.B.I. in an unrelated investigation, Mr. Trump invoked his Fifth Amendment right while openly questioning the legitimacy of the legal process — as he has with the nation’s electoral system — and insulting a law enforcement official sitting just a few feet away.