Idaho Code § 19-3005
If at the hearing the judge determines that the witness is material and necessary, that it will not cause undue hardship to the witness to be compelled to attend and testify in the prosecution in the other state, and that the laws of the state in which the prosecution is pending and of any other state through which the witness may be required to pass by ordinary course of travel, will give to him protection from arrest and the service of civil and criminal process he shall issue a subpoena, with a copy of the certificate attached, directing the witness to attend and testify in the court where the hearing or prosecution is pending at a time and place specified in the subpoena.
If the witness, who is subpoenaed as above provided, after being tendered by some properly authorized person a prepaid, round trip airline ticket or, in the event that there is no regularly scheduled airline service available, a prepaid round trip ticket on any common carrier providing passenger transportation services to and from the court where the hearing or prosecution is pending and five dollars ($5.00) for each day that he is required to travel and attend as a witness, fails without good cause to attend and testify as directed in the subpoena, he may be punished in the manner provided for the punishment of any witness who disobeys a subpoena issued from a court of record in this state.
If the witness is subpoenaed to attend and testify in the criminal hearing or prosecution in this state he shall be tendered the sum of fifteen cents (15¢) a mile for each mile by the ordinarily traveled route, one (1) way, to and from the court where the hearing or prosecution is pending and five dollars ($5.00) for each day that he is required to travel and attend as a witness. A witness who has appeared in accordance with the provisions of the subpoena shall not be required to remain within this state a longer period of time than the period mentioned in the certificate, unless such extended period of time is obtained by the written consent of such witness.
If a person passes through this state while going to another state in obedience to a subpoena to attend and testify in a criminal hearing or prosecution in that state or while returning therefrom, he shall not while so passing through this state be subjected to arrest or the service of process, civil or criminal, in connection with any matter which arose before his entrance into this state under such subpoena.
Idaho Code § 19-3005