Relevancy of statements: signed summons replies may be admissible in prosecutions when maker is unavailable or court permits in justice. Statements made and signed in response to a summons under section 70 are admissible to prove their truth when the maker is dead, cannot be found, is incapable of giving evidence, is kept away by the adverse party, or where securing the maker's presence would cause unreasonable delay or expense, and may also be admitted when the maker is examined and the court deems admission necessary in the interest of justice.