N.H. Rev. Stat. Ann. § 541:14

No new or additional evidence shall be introduced in the supreme court, but the case shall be determined upon the record and evidence transferred, except that in any case, if it shall be necessary in order that no party shall be deprived of any constitutional right, or if the court shall be of the opinion that justice requires the reception of evidence of facts which have occurred since the hearing, or which by reason of accident, mistake, or misfortune could not have been offered before the commission, it shall remand the case to the commission to receive and consider such additional evidence.