Although subsequent remedial measures are not barred by Federal Rule of Evidence 407 if they are offered to impeach a witness or to show a matter other than negligence, culpable conduct, a defect in a product, a defect in a product's design, or a need for a warning or instruction, the trial court has the discretion to exclude subsequent remedial measures when offered for such a permissible purpose if the trial court believes that the risk of the use of such evidence for such a purpose outweighs the probative value of the evidence.

United States v. Honken, 378 F. Supp. 2d 970, 983-984 (N.D. Iowa 2004) (trial court bars cross-examination about uncharged acts of indecent exposure by witness because such acts are not probative of truthfulness).Prior acts of a witness may be elicited during the interrogation of the witness to impeach the truthfulness of a witness, but the acts so inquired into must in fact be probative of truthfulness.

Cf. Schindler v. Joseph C. Seiler & Synthes Spine Co., L.P., 474 F.3d 1008, 1011-1012 (7th Cir. 2007) (holding, in plaintiff physician's diversity action against defendants individual and employer, that plaintiff's testimony about what Dr. White had said to him....For purposes of the hearsay exceptions created by Federal Rule of Evidence 804 or a comparable State rule, a declarant is "unavailable" within the meaning of Rule 804(a) or a comparable State rule if the declarant testifies to a lack of memory of the subject matter of the declarant's statement; but a declarant is not "unavailable" if such claim of lack of memory is due to the procurement or wrongdoing of the proponent of a statement for the purpose of preventing the witness from attending or testifying.

United States v. Guidry, 456 F.3d 493, 500-501 (5th Cir. 2006) (upholding trial court's admission of accused's other sexual assaults because, even though accused had not been convicted for the said offenses, Rule 413 does not limit admissibility of evidence of the act of doing or perpetrating other sexual...Federal Rule of Evidence 413(d) provides that for purposes of Rule 413 and also for purposes of Federal Rule of Evidence 415 an "offense of sexual assault" is 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; (2) contact, without consent, between any part of the defendant's body or an object and the genitals or anus of another person; (3) contact, without consent, between the genitals or anus of the defendant and any part of another person's body; (4) deriving sexual pleasure or gratification from the infliction of death, bodily injury, or physical pain on another person; or (5) an attempt or conspiracy to engage in conduct described in paragraphs (1)-(4).