The principle of multiple admissibility: if evidence is inadmissible for one purpose, it may be admissible for another purpose; if evidence is inadmissible to show one fact, the evidence, if relevant to another fact, may be admissible to show the other fact.

Fed. R. Evid. 602 advisory committee's note ("It will be observed that the rule [requiring personal knowledge] is in fact a specialized application of the provisions of Rule 104(b) on conditional relevancy.").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.

United States v. Malik, 928 F.2d 17, 22 (1st Cir. 1991) (conviction for conspiracy to import heroin and for importing heroin; on appeal, accused argued that the government used his statement to another person that accused had previously participated in a bad act, which in turn helped to show his bad...The principle of multiple admissibility: if evidence is inadmissible for one purpose, it may be admissible for another purpose; if evidence is inadmissible to show one fact, the evidence, if relevant to another fact, may be admissible to show the other fact.

Fed. R. Evid. 414(d) ("For purposes of this rule and Rule 415..., an "offense of child molestation" means a crime under Federal law or the law of a State (as defined in section 513 of title 18, United States Code) that involved-- (1) any conduct proscribed by chapter 109A of title 18, United States Code, that was committed in relation to...Applicable federal or state law determines what constitutes "child molestation" or "child sexual abuse" for purposes of Federal Rule of Evidence 414 or comparable State rules that authorize the use of other instances of child molestation or child sex abuse against criminal defendants who are on trial for child molestation or child sexual abuse.