Does an impermissible rebuttal argument violate the Fifth Amendment?

We review de novo the question of whether an impermissible rebuttal argument violates the Fifth Amendment. United States v. Gray, 876 F.2d 1411, 1416 (9th Cir.1989), cert. denied, 495 U.S. 930 (1990).

"A prosecutorial statement is impermissible if it is manifestly intended to call attention to the defendant's failure to testify, or is of such a character that the jury would naturally and necessarily take it to be a comment on the failure to testify.' " Gray, 876 F.2d at 1416 (citation omitted). "A comment on the failure of the defense as opposed to the defendant to counter or explain the testimony presented or evidence introduced is not an infringement of the defendant's Fifth Amendment privilege." United States v. Castillo, 866 F.2d 1071, 1083 (9th Cir.1988) (citations omitted).