Rule 103(b) Offer of proof—Form. R103(b) accords the trial judge discretion as to the form of an offer of proof. A formal offer, in question-and-answer form, is a more reliable method. A question-and-answer offer eliminates doubt as to the harm caused by the exclusion, and may encourage the trial judge to reconsider the ruling. An opponent may request that the court direct the question-and-answer form in order to "call the bluff' of a proponent whose avowal may be optimistic.
Example. "To answer the standard of review, we must first determine whether Silver Mountain made the requisite offer of proof. An offer of proof is necessary to permit the trial judge to make an informed evidentiary ruling as well as `to create a clear record that an appellate court can review to "determine whether there was reversible error in excluding the [testimony]." ' But ' "merely telling the court of the content of * * * proposed testimony" is not an offer of proof.' Instead, the proponent must `describe the evidence and what it tends to show and * * * identify the grounds for admitting the evidence.' Where both proper and improper purposes for proffered evidence exist, the offer of proof must rule out the improper purposes because the trial judge is not required to 'imagine some admissible purpose.' Finally, Rule 103 does not require any specific form for offers of proof. Instead the trial judge has discretion to shape the manner and form of the offer of proof. We agree the district court did not err in excluding the evidence. While given ample opportunity, Silver Mountain failed to make an adequate offer of proof concerning the content and admissibility of the August 2005 cell phone payment, so plain error review governs." Perkins v. Silver Mt. Sports Club & Spa, LLC, 557 F.3d 1141, 1147-49 (10th Cir.2009) (citations omitted).
R104 The most common example of a situation of "conditional relevancy" is authentication or identification. The authentication of a document or an item of real evidence requires evidence sufficient to support a jury finding that the offered item is what its proponent claims. The function of the judge is merely to determine whether a prima facie case has been presented, not to decide the actual issue of genuineness. This traditional doctrine is codified not only in Rule 104(b), but also in Rule 901(a). Ricketts v. City of Hartford, 74 F.3d 1397, 1409-11 (2d Cir.1996).