Today's new word is "bonafy."
1 : to prove good faith or earnest intent
2 : to authenticate or certify as authentic
When someone makes a seemingly outrageous or unbelievable assertion, a proper response might be something like:
"Can you cite a reference with which to bonafy that statement? Without some kind of proof, I cannot consider your statement to be bona fide."
A document such as a witness' testimony might require supporting documentation including a writ of bonafication.