@Deckard,
People always say that "a fact is a fact"
but
The facts about a physical process or a chemical reaction can be directly demonstrated.
The facts about history or a historical process (evoloution, cosmology) can not be directly demonstrated.
The law deals more with evidence, verdicts and precedents than with facts.
Some evidence consists of facts of various kinds and with various degrees of reliability. Eye witness descriptions (notroiously inaccurate), videotape pretty good, fiber analysis, fingerprints and blood types (not so good), DNA fingerprints (pretty good).
The verdicts in a courtroom (not always justice, not always based on truth). For criminal cases "beyond the shadow of a doubt", for civil cases "the preponderance of evidence". Not all facts are equal and not all truth is equally reliable or equally confirmed.