What is the test for knowing or should have known that a victim of the crime was unusually vulnerable?

Section 3A1.1 applies if "the defendant knew or should have known that a victim of the offense was unusually vulnerable due to age, physical or mental condition, or that a victim was otherwise particularly susceptible to the criminal conduct." In this case, the district judge focused on the final clause: "that a victim was otherwise particularly susceptible." Unlike the factors specified for vulnerability, this language does not limit the reasons for finding a victim vulnerable. United States v. Hershkowitz, 968 F.2d 1503, 1506 (2d Cir.1992). In assessing whether the victim is susceptible to the criminal conduct, the court must consider the totality of the circumstances, including the victim's physical and financial condition and the nature of the crime. Id.