(i) The reason the position exists is to perform the function;
(ii) Limited number of employees are available among whom the performance of that job function can be distributed; and/or
(iii) The function may be highly specialized so that the person is hired for their expertise or ability to perform the particular function.
(i) The employer's judgment;
(ii) Written job descriptions prepared before advertising or interviewing applicants for the job;
(iii) The amount of time spent on the job in performing the functions;
(iv) The consequences of not requiring the incumbent to perform the functions;
(v) The work experience of past incumbents in the job; and/or
(vi) The current work experience of incumbents in similar jobs.
"Marginal Functions" is defined as:
The ADA focuses on job performance and not marginal duties in determining what is an essential job function.
A federal court held that answering the telephone was not an essential function of a time-and-attendance clerk at the post office. They found that the clerk was responsible for tallying, documenting, and analyzing the hours that postal service employees worked. Therefore, it would be discrimination not to hire an otherwise qualified individual who is deaf or has a speech disability.