～はずです
You can say something is “supposed to be the case,” by adding はずです to a sentence ending in the short form.
Ex: きのうメアリーさんはどこにもいかなかったはずです。 (I believe that Mary did not go anywhere yesterday.)
You can turn はずです into the past tense to describe something that was supposed to have been the case but which actually turned out otherwise. The part that precedes はずでした is in the present tense.