29 CFR 18.104 - Preliminary questions.
(a) Questions of admissibility generally. Preliminary questions concerning the qualification of a person to be a witness, the existence of a privilege, or the admissibility of evidence shall be determined by the judge, subject to the provisions of paragraph (b) of this section. In making such determination the judge is not bound by the rules of evidence except those with respect to privileges.
(b) Relevance conditioned on fact. When the relevancy of evidence depends upon the fulfillment of a condition of fact, the judge shall admit it upon, or subject to, the introduction of evidence sufficient to support a finding of the fulfillment of the condition.
(c) Weight and credibility. This rule does not limit the right of a party to introduce evidence relevant to weight or credibility.