Does compelled discovery of statements of defense witnesses implicate the self-incrimination clause?

8 In determining whether the compelled discovery of statements of defense witnesses implicates the self-incrimination clause, we have thus far focused on the materials actually disclosed. We also note, however, that the act of handing over the statements of defense witnesses to the prosecutor does not implicate the privilege. This act is not "testimonial or communicative in nature" because the act itself does not "reveal, directly or indirectly, [defendant's] knowledge of facts relating him to the offense or ... [require defendant] to share his thoughts and beliefs with the Government." (Doe v. United States, supra, 487 U.S. 201, 213, 108 S.Ct. 2341, 2349, italics added.)