Generally, employers are under no obligation to determine whether or not an employee's poor work performance may be caused by a disability. However, if the employer has received notice that the employee has a disability protected by the Americans with Disabilities Act (ADA), the employer may have an obligation to find a reasonable accommodation prior to taking disciplinary action against the employee or firing the employee for performance problems.
Many conditions that may affect an employee's performance may not be visually obvious, but still may receive protection under the ADA as a disability. However, if the employee does not link the performance problem to his or her disability, then the employer is not required to assume that they are related.
Furthermore, if no reasonable accommodation exists or is effective in improving the employee's performance, the employer is not required to lower the expectations for job performance to accommodate the employee and to avoid termination. Nor are they required to have other’s perform some of the employee’s job duties as an accommodation. If there is no reasonable accommodation and the work cannot be done by the employee, a termination may be permitted. However proper documentation will be needed at all phases of the investigation