Relevancy of statements: summoned declarations may be admitted in GST prosecutions when the declarant is unavailable or court permits. A signed statement made on appearance in response to a summons under section 70 is admissible in prosecutions when the declarant is dead, cannot be found, is incapable of giving evidence, has been kept away by an adverse party, or when securing the declarant's presence would cause unreasonable delay or expense; additionally, the court may admit such a statement when the declarant is examined as a witness if admission is, in the court's view, in the interest of justice.