The "declarant" must be a person. For purposes of the federal hearsay rule a "declarant" cannot be a machine, a physical process, or any other non-human process.

Upjohn Co. v. United States, 449 U.S. 383, 389 (1981) ("The attorney-client privilege is the oldest of the privileges for confidential communications known to the common law. 8 J. Wigmore, Evidence ? 2290 (McNaughton rev. 1961). Its purpose is to encourage full and frank communication between attorneys...Various purposes have been imputed to the attorney-client privilege. The most common purpose attributed to the privilege is facilitation of the exchange of information between client and attorney to promote the giving of well-informed and factually-based legal advice and services, which are seen as beneficial to society.

United States v. Sinclair, 109 F.3d 1527, 1536-1537 (10th Cir. 1997) ("Although Rule 602 provides that a witness's testimony must be based on personal knowledge, it 'does not require that the witness' knowledge be positive or rise to the level of absolute certainty. Evidence is inadmissible ... only if...A person has the personal knowledge that a witness must have if and only if the evidence is sufficient to permit a reasonable trier of fact to conclude that the witness personally perceived the matter. The preliminary question of personal knowledge is governed by the standard of whether the evidence is sufficient to allow a reasonable person to conclude that the person has personal knowledge; the applicable standard is not the more demanding preponderance of the evidence standard.

Fed. R. Evid. 403 ("Although relevant, evidence may be excluded if its probative value is substantially outweighed by the danger of unfair prejudice").The trial court may exclude relevant and probative evidence as unduly prejudicial if it concludes that the evidence presents the risk of juror emotion or passion and that this risk substantially outweighs the probative value of the evidence.