Witnesses, other than law enforcement officers testifying in their official capacity, in the Supreme Judicial Court, the Superior Court, the District Court or in the Probate Court, unless the court otherwise orders, must receive $10, and before referees, auditors or commissioners specially appointed to take testimony or special commissioners on disputed claims appointed by Probate Courts, $10, or before the county commissioners, $10 for each day’s attendance and 22¢ a mile for each mile’s travel going and returning home. The party calling the witness shall pay the witness. Payments made under this section to witnesses called on behalf of the State must be made from the county treasury upon authorization of the prosecuting attorney, unless otherwise directed by law. The court in its discretion may allow at the trial of any cause, civil or criminal, in the Supreme Judicial Court, the Superior Court or the District Court, a reasonable sum for each day’s attendance of any expert witness or witnesses at the trial, in taxing the costs of the prevailing party, and the expense of all expert witnesses for the State in murder cases must be paid by the State and charged against the appropriation for the Department of the Attorney General. Such party or the attorney of record shall first file an affidavit within 30 days after entry of judgment and before the cause is settled, stating the name, residence, number of days in attendance and the actual amount paid or to be paid each expert witness in attendance at such trial. No more than $10 per day may be allowed or taxed by the clerk of courts in the costs of any civil action for the per diem attendance of a witness, unless the affidavit is filed, and the per diem is determined and allowed by the presiding justice. [PL 2007, c. 539, Pt. JJ, §7 (AMD); PL 2007, c. 539, Pt. JJ, §10 (AFF).]