Employers are not allowed by law to discriminate against people with disabilities. When employers want to recruit people to join them, they are forbidden from excluding any disabled person. Title I of the ADA provides rules for employers who have fifteen or more full or part time employees. However, this doesn't mean that the disabled person is always the best person for the job, or that if the disabled person doesn't get the job it's because of their disability.
The rights apply to disabled people who qualify under the ADA, whether or not they need to be ‘reasonably accommodated' in order to carry out the essential requirements of the job description. At this point, it's worth defining the word ‘qualify'. A qualified person is able to carry out the required functions of a job. That means that they are capable of doing the fundamental aspects of a job. However, employers should not be inflexible as to what the essential functions are and the time spent on each aspect. Indeed, employers must make ‘reasonable accommodation' for those with disabilities, which cover not only physical access but also the adaptation of equipment, training materials and work schedules, amongst other things.
If you have a disability and need an accommodation in order to carry out your job, it is your responsibility to request it. It's important to remember, though, that an employer does not have to go to the expense of the accommodation if it would put an unfair financial or administrative strain on them.
So where is the line drawn between not choosing or not being able to employ a disabled person, and actively discriminating against them? An employer is not permitted to ask any questions about your health at all until after you have been offered a job. You can only be asked to take a test if people with the same or similar roles are also tested. Once you're in a job, you are entitled to the same insurance, training and benefits as everyone else. If an insurer doesn't insure someone with your disability, your employer must find another insurer. However, rights under the ADA don't stop with the person who is disabled. An employer is not allowed to discriminate against someone who is connected to someone with a disability, for example a spouse or child.
Of course there are also health and safety issues. For example, an employer would not have to hire a disabled person if there was a direct and unavoidable risk to other employees. However, this threat must be ‘immediate' and ‘significant' and not just theoretical. Then again, if being able-bodied is an absolutely essential requirement of the job, this would cover the ‘essential elements' factor in the ADA and so a disabled person would not have grounds to file a discrimination lawsuit. For example, being a delivery truck driver in which you made numerous stops each day to load and offload goods would be unsuitable for someone who uses a wheelchair.
If you feel that you have been unfairly treated in your job or during the application process, because you or someone you know has a disability, you should speak to an attorney.