Idaho Code § 19-3008
When a person shall attend before a grand jury, or the district court, as a witness, upon a subpoena, or pursuant to an undertaking, such person shall receive the same rate per mile as the state of Idaho pays for state employees pursuant to section 67-2008, Idaho Code, but no person can receive more than one (1) mileage under this section per day of attendance in court; such person shall also receive eight dollars ($8.00) per day for each day's actual attendance as such witness and reasonable lodging expenses when approved in advance by the judge before whom the witness appears. Such mileage and per diem must be paid out of the county treasury of the county where such district court is held, upon the certificate of the clerk of said court: provided, however, that when a defendant in a criminal proceeding requires the attendance of more than five (5) witnesses in his behalf, before such witnesses shall be subpoenaed at the county's expense, or their fees and mileage be a charge against the county, such defendant must make affidavit setting forth that they are witnesses whose evidence is material to his defense, and that he can not safely go to trial without them. In such case the court, or the judge thereof, at any time application is made therefor, shall order a subpoena to issue to such of said witnesses as the court, or the judge thereof, may deem material for the defendant, and the costs incurred by the process and the fees and mileage of such witnesses shall be paid in the same manner that the costs and fees of other witnesses are paid.
Idaho Code § 19-3008