Source: http://masslitapp.com/html/Federal_Rules_of_Evidence/062017/Federal_Rules_of_Evidence_062017Rule_104.html
Timestamp: 2019-04-18 20:38:19+00:00

Document:
(a) In General. The court must decide any preliminary question about whether a witness is qualified, a privilege exists, or evidence is admissible. In so deciding, the court is not bound by evidence rules, except those on privilege.
(b) Relevance That Depends on a Fact. When the relevance of evidence depends on whether a fact exists, proof must be introduced sufficient to support a finding that the fact does exist. The court may admit the proposed evidence on the condition that the proof be introduced later.
(d) Cross-Examining a Defendant in a Criminal Case. By testifying on a preliminary question, a defendant in a criminal case does not become subject to cross-examination on other issues in the case.
(e) Evidence Relevant to Weight and Credibility. This rule does not limit a party’s right to introduce before the jury evidence that is relevant to the weight or credibility of other evidence.
Subdivision (a). The applicability of a particular rule of evidence often depends upon the existence of a condition. Is the alleged expert a qualified physician? Is a witness whose former testimony is offered unavailable? Was a stranger present during a conversation between attorney and client? In each instance the admissibility of evidence will turn upon the answer to the question of the existence of the condition. Accepted practice, incorporated in the rule, places on the judge the responsibility for these determinations. McCormick §53; Morgan, Basic Problems of Evidence 45–50 (1962).
To the extent that these inquiries are factual, the judge acts as a trier of fact. Often, however, rulings on evidence call for an evaluation in terms of a legally set standard. Thus when a hearsay statement is offered as a declaration against interest, a decision must be made whether it possesses the required against-interest characteristics. These decisions, too, are made by the judge.
In view of these considerations, this subdivision refers to preliminary requirements generally by the broad term “questions,” without attempt at specification.
This subdivision is of general application. It must, however, be read as subject to the special provisions for “conditional relevancy” in subdivision (b) and those for confessions in subdivision (d).
This view is reinforced by practical necessity in certain situations. An item, offered and objected to, may itself be considered in ruling on admissibility, though not yet admitted in evidence. Thus the content of an asserted declaration against interest must be considered in ruling whether it is against interest. Again, common practice calls for considering the testimony of a witness, particularly a child, in determining competency. Another example is the requirement of Rule 602 dealing with personal knowledge. In the case of hearsay, it is enough, if the declarant “so far as appears [has] had an opportunity to observe the fact declared.” McCormick, §10, p. 19.
Rule 4(g) provides for proof of service by affidavit. Rule 56 provides in detail for the entry of summary judgment based on affidavits. Affidavits may supply the foundation for temporary restraining orders under Rule 65(b).
Subdivision (b). In some situations, the relevancy of an item of evidence, in the large sense, depends upon the existence of a particular preliminary fact. Thus when a spoken statement is relied upon to prove notice to X, it is without probative value unless X heard it. Or if a letter purporting to be from Y is relied upon to establish an admission by him, it has no probative value unless Y wrote or authorized it. Relevance in this sense has been labelled “conditional relevancy.” Morgan, Basic Problems of Evidence 45–46 (1962). Problems arising in connection with it are to be distinguished from problems of logical relevancy, e.g. evidence in a murder case that accused on the day before purchased a weapon of the kind used in the killing, treated in Rule 401.
If preliminary questions of conditional relevancy were determined solely by the judge, as provided in subdivision (a), the functioning of the jury as a trier of fact would be greatly restricted and in some cases virtually destroyed. These are appropriate questions for juries. Accepted treatment, as provided in the rule, is consistent with that given fact questions generally. The judge makes a preliminary determination whether the foundation evidence is sufficient to support a finding of fulfillment of the condition. If so, the item is admitted. If after all the evidence on the issue is in, pro and con, the jury could reasonably conclude that fulfillment of the condition is not established, the issue is for them. If the evidence is not such as to allow a finding, the judge withdraws the matter from their consideration. Morgan, supra; California Evidence Code §403; New Jersey Rule 8(2). See also Uniform Rules 19 and 67.
The order of proof here, as generally, is subject to the control of the judge.
Subdivision (c). Preliminary hearings on the admissibility of confessions must be conducted outside the hearing of the jury. See Jackson v. Denno, 378 U.S. 368, 84 S.Ct. 1774, 12 L.Ed.2d 908 (1964). Otherwise, detailed treatment of when preliminary matters should be heard outside the hearing of the jury is not feasible. The procedure is time consuming. Not infrequently the same evidence which is relevant to the issue of establishment of fulfillment of a condition precedent to admissibility is also relevant to weight or credibility, and time is saved by taking foundation proof in the presence of the jury. Much evidence on preliminary questions, though not relevant to jury issues, may be heard by the jury with no adverse effect. A great deal must be left to the discretion of the judge who will act as the interests of justice require.
Subdivision (d). The limitation upon cross-examination is designed to encourage participation by the accused in the determination of preliminary matters. He may testify concerning them without exposing himself to cross-examination generally. The provision is necessary because of the breadth of cross-examination under Rule 611(b).
Subdivision (e). For similar provisions see Uniform Rule 8; California Evidence Code §406; Kansas Code of Civil Procedure §60–408; New Jersey Evidence Rule 8(1).
Rule 104(c) as submitted to the Congress provided that hearings on the admissibility of confessions shall be conducted outside the presence of the jury and hearings on all other preliminary matters should be so conducted when the interests of justice require. The Committee amended the Rule to provide that where an accused is a witness as to a preliminary matter, he has the right, upon his request, to be heard outside the jury's presence. Although recognizing that in some cases duplication of evidence would occur and that the procedure could be subject to abuse, the Committee believed that a proper regard for the right of an accused not to testify generally in the case dictates that he be given an option to testify out of the presence of the jury on preliminary matters.
The Committee construes the second sentence of subdivision (c) as applying to civil actions and proceedings as well as to criminal cases, and on this assumption has left the sentence unamended.
Under rule 104(c) the hearing on a preliminary matter may at times be conducted in front of the jury. Should an accused testify in such a hearing, waiving his privilege against self-incrimination as to the preliminary issue, rule 104(d) provides that he will not generally be subject to cross-examination as to any other issue. This rule is not, however, intended to immunize the accused from cross-examination where, in testifying about a preliminary issue, he injects other issues into the hearing. If he could not be cross-examined about any issues gratuitously raised by him beyond the scope of the preliminary matters, injustice result. Accordingly, in order to prevent any such unjust result, the committee intends the rule to be construed to provide that the accused may subject himself to cross-examination as to issues raised by his own testimony upon a preliminary matter before a jury.
The amendments are technical. No substantive change is intended.
The language of Rule 104 has been amended as part of the restyling of the Evidence Rules to make them more easily understood and to make style and terminology consistent throughout the rules. These changes are intended to be stylistic only. There is no intent to change any result in any ruling on evidence admissibility.

References: §53
 §10
 §403
 v. 
 §406
 §60