Rule 104 of the Tennessee Rules of Evidence permits the trial judge significant leeway in what may be considered in determining what evidence can be admitted at trial. It provides as follows:
Rule 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 court, subject to the provisions of subdivision (b). In making its determination the court is not bound by the rules of evidence except those with respect to privileges.
Here is subdivision (b):
(b) Relevance Conditioned on Fact. —When the relevance of evidence depends on the fulfillment of a condition of fact, the court shall admit it upon the introduction of evidence sufficient to support a finding of the fulfillment of the condition. In the court’s discretion, evidence may be admitted subject to subsequent introduction of evidence sufficient to support a finding of the fulfillment of the condition.
Here is the Advisory Commission Comment:
Part (a) governs the fact questions to be resolved by trial courts in deciding whether a sufficient foundation has been laid. For example, the court must decide that the declarant believed death was imminent in order to admit a dying declaration. This preliminary determination can be based on hearsay, because the judge should be able to separate reliable from unreliable proof.
Part (b) allows the court to admit evidence over a relevancy objection on condition that the offering party prove other facts making the evidence relevant. If subsequent proof fails to establish relevancy, the conditionally admitted evidence should be stricken with an appropriate jury instruction; extreme prejudice could result in a mistrial.
Thus, lawyers may depend on classic hearsay, learned treatises, and other data not otherwise admissible in evidence in Tennessee to persuade a judge to admit other evidence. One classic area where this rule can be used is proof of "the same or similar community" in medical negligence cases.