Relevancy of statements in GST prosecutions when declarant is unavailable or court admits prior signed statement in interest of justice. Section 136 makes statements made and signed on appearance in response to a summons under section 70 relevant in prosecutions under the Act when the declarant is unavailable to give evidence because of death, absence, incapacity, being kept away by an adverse party, or when obtaining presence would cause unreasonable delay or expense; it also permits admission when the declarant is examined and the court, in the circumstances, admits the statement in the interest of justice.