Whether a District Court's decision allowing a witness called by a criminal defendant to refuse to testimony based on his claimed Fifth Amendment privilege is subject to 'abuse of discretion' review or de novo review, and whether such a decision violates the defendant's Sixth Amendment rights

1. Whether a District Court’s decision allowing a witness called by a criminal defendant to refuse to testify based on his claimed Fifth Amendment privilege is subject to “abuse of discretion” review by the Court of Appeals, because it presents merely an evidentiary issue, as the Fourth Circuit held, or is subject to “de novo” review, because it involves the analysis of the conflicting Constitutional rights of the witness and the defendant , as the Tenth Circuit has held? 2. If “abuse of discretion” is the proper standard, whether a district court abuses that discretion and thereby violates a criminal defendant’s Sixth Amendment rights, when, as here, it allows a witness called by the defendant to refuse to testify, even though the witness's conviction was final and he would not have any legal exposure unless his sentence were first reversed by the Court of Appeals , in the absence of any plausible grounds for reversal, and, even then, it would be implausible that he could receive a lesser sentence. ii List of