From Longman Dictionary of Contemporary Englishthe facts speak for themselvesthe facts speak for themselvesused to say that the things that have happened or the things someone has done show clearly that something is true → fact
Examples from the Corpus
the facts speak for themselves• She obviously knows what she's doing - the facts speak for themselves.• Concerning investigation into the conditions endured by animals in laboratories, the facts speak for themselves.• Mark answered in the traditional matter-of-fact manner, parading all the relevant factors and letting the facts speak for themselves.• In such a case the purchaser may plead res ipsa loquitur - the facts speak for themselves.• Autoseeker speaks to the thief - the facts speak for themselves. 