You can't expect me to believe that
you can't expect (one) to believe (something)
What you are saying is absolutely ridiculous or wholly unbelievable, and there is no way one will believe it. Try giving a more straightforward excuse as to why you can't come into work today. You can't expect your boss to believe such a bizarre story. A: "I finished my homework, mowed the lawn, did the dishes, and cleaned my room!" B: "In the span of an hour? Ha! You can't really expect me to believe that, can you?"
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
You can't expect me to believe that.and You don't expect me to believe that.
That is so outrageous that no one could believe it. Bill: My father is running for president. Bob: You can't expect me to believe that. Jane: Everyone in our family has one extra toe. Mary: You don't expect me to believe that!
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs. © 2002 by The McGraw-Hill Companies, Inc.