Whenever the court is satisfied by appropriate evidence or by agreement of counsel that the United States or the claimant is unable after reasonable efforts to secure the testimony of a witness and—
((1)) the United States or the claimant has been prevented by a stay under this chapter from examining the witness; or
((2)) the United States establishes that it has refrained from bringing a suit or from taking the testimony of the witness in a pending suit to avoid endangering the security of naval operations or interfering with such operations;
((1)) the affidavit of the witness duly sworn to before a notary public or other authorized officer; or
((2)) the statement or testimony of the witness before a court-martial, a court of inquiry, or an investigation; but the use of such statement or testimony does not, in any litigation, make the remainder of the record admissible or compel the United States to produce the remainder of the record.