28 U.S.C. § 2246 : US Code - Section 2246: Evidence; depositions; affidavits

Search 28 U.S.C. § 2246 : US Code - Section 2246: Evidence; depositions; affidavits

On application for a writ of habeas corpus, evidence may be taken
orally or by deposition, or, in the discretion of the judge, by
affidavit. If affidavits are admitted any party shall have the
right to propound written interrogatories to the affiants, or to
file answering affidavits.