What is the test for establishing habit under Rule 406?

A district court's ruling on whether proffered evidence qualifies as habit evidence under Federal Rule of Evidence 406 is highly fact-specific. See Mathes v. The Clipper Fleet, 774 F.2d 980, 984 (9th Cir. 1985) (noting that examples of conduct submitted for the purpose of establishing habit must be "carefully scrutinized" to ensure that they are numerous enough to justify an inference of systematic conduct). Because factual matters predominate in determining whether certain evidence sought to be introduced at trial qualifies as habit under Rule 406, we will employ an abuse of discretion standard.