Benson involves a worker who was fired by NW after not being able to find another position in the 90 days given to him. Important info from case about determining what essential functions are:
Although Benson retains the ultimate burden of persuading the trier of fact that he can perform the essential functions of the job, with or without accommodation, much of the information which determines those essential functions lies uniquely with the employer. For example, the ADA and its implementing regulations direct us to consider, among other things, the following: “the employer's judgment as to what functions of a job are essential,” 42 U.S.C. § 12111(8); job descriptions prepared before advertising or interviewing applicants, id.; “[t]he consequences of not requiring the [employee] to perform the function,” 29 C.F.R. § 1630.2(n)(3)(iv) (1994); and the work experience of current and former employees. 29 C.F.R. § 1630.2(n)(3)(vi), (vii) (1994).