What is the current state of the law on the admissibility of a warning statement in a Miranda case?

Oregon v. Elstad, supra, 470 U.S. 298 rejected a "cat out of the bag" approach dictating that once an unwarned statement is made a subsequent warned statement is inadmissible because a person cannot effectively take back what she or he has said. Elstad instead held that "though Miranda requires that the unwarned admission must be suppressed, the admissibility of any subsequent statement should turn in these circumstances solely on whether it is knowingly and voluntarily made." (Oregon v. Elstad, supra, 470 U.S. at p. 309.)