“ On the other hand, a statute is not ex post facto which mitigates instead of increasing punishment, or which changes the rules of evidence or procedure in matters of detail without impairing any substantial right which the law gave the accused at the time when his alleged criminal act was done. ”

“ In conclusion, it should be remembered that the constitutional provisions in question have always received a liberal construction, with the view of giving full effect to this avowed purpose of protecting the individual right of life and liberty against hostile retrospective legislation. ”