Admission of otherwise inadmissible evidence in response to opponent's use of inadmissible evidence or improper inferences

Cf. United States v. Armijo, 5 F.3d 1229, 1232-1233 (9th Cir. 1993) (holding that the trial court erred in admitting a witness's unsworn prior inconsistent statement "because it was not given under oath." but "the admission of....A prior inconsistent statement of a witness is admissible, not only to impeach the witness, but also as substantive evidence -- to prove the truth of the matter previously asserted by the witness -- only if the prior consistent statement was made under oath.

Fed. R. Evid. 602 advisory committee's note (("[T]he rule requiring that a witness who testifies to a fact which can be perceived by the senses must have had an opportunity to observe, and must have actually observed the fact" is a 'most pervasive manifestation' of the common law insistence upon 'the most reliable sources of information.'...A person may testify to a matter only if there is sufficient evidence to show that the person has personal knowledge of the matter.

Croskey v. BMW of North America, Inc., 532 F.3d 511, 518 (6th Cir. 2008).To be admissible, prior events or accidents must be substantially similar to those at issue in trial.