The 5th Ammendment and Respect for the Truth

A random thought:

The 5th Ammendment to our Constitution in the United States reads in part, "...nor shall [any person] be compelled in any criminal case to be a witness against himself..."

One of the very interesting things about this, it strikes me, is that it implicitly assumes that a certain, perhaps significant, portion of defendants would not simply lie under oath if asked questions that could incriminate themselves. That is, of course, the modern assumption. But it seems to me that the fact that this was included in the 5th Ammendment shows the Framers actually thought that, under oath, people would feel compelled to tell the truth, even if it hurt them.