Davis v. Swarthout, 2012 U.S. Dist. LEXIS 15630 (E.D. Cal. Feb. 7, 2012):

Federal Rule of Evidence 404, as does its counterpart, California Evidence Code § 1101, generally prohibits the introduction of evidence of extrinsic acts that might adversely reflect on the actor's character, unless that evidence bears upon a relevant issue in the case such as motive, opportunity, or knowledge. No preliminary showing is necessary before such evidence may be introduced for a proper purpose. [Huddleston v. United States, 485 U.S. 681, 687-88 (1988) (citing Fed. R. Evid. 404).] If offered for such a proper purpose, the evidence is subject only to general strictures limiting admissibility such as Federal Rules of Evidence 402 and 403.

There is a split among the circuit courts as to the proper standard of review, de novo or abuse of discretion, to be applied to the question of whether evidence falls within the scope of Rule 404(b). The Ninth Circuit applies a de novo standard [United States v. Montgomery, 384 F.3d 1050, 1061 (9th Cir. 2004)], while the Second Circuit applies an abuse of discretion standard. 81 California employs an abuse of discretion standard on appellate review of § 1101(b) rulings [United States v. Paulino, 445 F.3d 211, 221 (2d Cir. 2006)]. The Supreme Court has held that in ruling on whether evidence is properly admitted under Rule 404(b) the court must consider whether: (1) the prior acts evidence was offered for a proper purpose; (2) the evidence was relevant to a disputed issue; (3) the probative value of the prior act evidence substantially outweighed the danger of its unfair prejudice; and (4) whether the court, if requested, administered an appropriate limiting instruction. [Huddleston, 485 U.S. at 691-92] Under California Evidence Code § 1102(b), as "circumstantial evidence, its admissibility depends upon three principal factors: (1) the materiality of the fact sought to be proved or disproved; (2) the tendency of the uncharged crime to prove or disprove the material fact; and (3) the existence of any rule or policy requiring the exclusion of relevant evidence."