WASHINGTON — The epic fight between the F.B.I. and Apple over a locked iPhone is now over, but a central question in the case has remained unanswered: What secrets did the phone, used by one of the attackers in the San Bernardino, Calif., rampage, actually hold?

The question has persisted with all the anticipation of Geraldo Rivera’s ill-fated unlocking of Al Capone’s secret vault on live television 30 years ago — which produced only a few empty liquor bottles and a stop sign.

On Tuesday, the F.B.I.’s top lawyer shed a bit more light on the question, a week after the Justice Department announced that it had gotten into the iPhone without Apple’s help. The lawyer, James A. Baker, the bureau’s general counsel, told an audience of privacy professionals in Washington that the F.B.I. had extracted data and was putting it to use.

He would not say, however, whether he considered the data — the subject of a monthlong legal battle between Apple and the F.B.I. that ended when an undisclosed outside firm helped investigators unlock the phone — to be “useful.”