Upon application of a party to a criminal case, a United States district court before which the case is pending may, to the extent permitted by a foreign country, appoint a special master to carry out at a deposition taken in that country such duties as the court may direct, including presiding at the deposition or serving as an advisor on questions of United States law. Notwithstanding any other provision of law, a special master appointed under this section shall not decide questions of privilege under foreign law. The refusal of a court to appoint a special master under this section, or of the foreign country to permit a special master appointed under this section to carry out a duty at a deposition in that country, shall not affect the admissibility in evidence of a deposition taken under the provisions of the Federal Rules of Criminal Procedure.