In the Bible or Mormon Doctrine is there a parable or some kind of
story about someone telling outrageous stories and everyone thinks he
is lying but later they check to see if he is telling the truth.  When
they find out he was telling the truth the moral of the story is do
not assume people are lying unless you check to see if they are
telling the truth.  Can you name the verse in the bible?

Could you be thinking of one of Aesop's fables, "The Boy Who Cried Wolf"?

http://tomsdomain.com/aesop/id87.htm

I have found a Biblical equivalent to The Boy Who Cried Wolf.  Click
on "Answer" under "The boy who cried wolf."

"Who Said It?"
E-geress
http://www.e-geress.org/wsi/wsi_3.htm

I think that both The Boy Who Cried Wolf and the Biblical equivalent
are a little different from the parable that you have described.  The
moral of these stories is not "do not assume people are lying", but
rather "do not lie".

But if you believe that this is the answer, I would be happy to post
it.

In the book of Alma (part of the Book of Mormon), there is a story
about Zeezrom, who tells outrageous lies. Later, when he hears people
speaking the truth, he feels guilty for what he has done and changes
his ways. I doubt if that's the story you're thinking of, but there's
a good lesson in there anyway.

There's Cassandra, "granted the gift of prophecy by Apollo, but
condemned never to be believed" (Encarta World English Dictionary) -
but of course, that's Greek mythology, not Bible parable.

If we catch a person telling several unrelated lies, we can hardly be
expected to invest lots of energy in testing future things this person
says. Society loses whenever lies are told, so please tell the truth,
avoid half truths and false inferences.   Neil