The justices ruled that an assembly line worker with carpal tunnel syndrome was not entitled to special treatment on the job.
A unanimous court ruled that Ella Williams' partial disability did not obligate her employer, car manufacturer Toyota, to tailor a job to suit her wrist, arm and shoulder problems.
The 1990 Americans With Disabilities Act guarantees equal treatment on the job and elsewhere for people whose disabilities "substantially limit" their ability to perform what the law calls "major life activities," such as caring for oneself.
But the controversial piece of legislation turned into a highly litigated and often disputed law pitting disabled and injured workers against employers, reports CBS News Correspondent Sandra Hughes.
"Had the court decided the other way, the implications would have been enormous for business in that every injury potentially could have qualified as a disability under the ADA," said Patrick Cleary of the National Association of manufacturers.
Williams' disability did not prevent her from doing many tasks at home and at work. But a federal appeals court found that she was disabled under the ADA because her physical problems substantially limited her ability to perform manual tasks at work.
"This was error," the Supreme Court noted in an opinion written by Justice Sandra Day O'Connor.
The decision was a victory for Toyota Motor Corp., which argued the appeals court applied the wrong test by ruling that the law covered an impairment preventing a worker from performing a particular job task.
This decision will be hailed by employers, says CBSNews.com Legal Analyst Andrew Cohen, because it narrows or limits the definition of "disability" within the meaning of the Americans with Disabilities Act, which means it will be harder for employees in the future to prove that they fall within the Act's protections.
In cases like Williams', "the central inquiry must be whether the claimant is unable to perform the variety of tasks central to most people's daily lives, not whether the claimant is unable to perform the tasks associated with her specific job," the court wrote.
Disability cannot be assessed by looking only at someone's fitness to work, the court said.
The court reversed the opinion of the Cincinnati-based 6th U.S. Circuit Court of Appeals and sent the Williams case back with instructions to reconsider it.
The ruling does not mean that anyone with carpal tunnel syndrome or similar partial disabilities is automatically excluded from protection by the ADA. But it probably will make such claims harder to prove, since the court makes clear that disability must affect a range of manual tasks or duties.
The court's rulig may affect millions of U.S. workers who suffer repetitive strain injuries or similar impairments that leave them partly disabled. Industry groups have said the case could have a significant impact on a broad range of businesses.
Williams and advocates for the disabled had argued that her case was emblematic of just the kind of discrimination the ADA was supposed to prevent.
A partially disabled person who wants to work should be able to do so, with modest accommodation by an employer, rather than being forced to sit home, her lawyers have argued.
Williams claimed that her work on a Toyota engine assembly line so damaged her hands and arms that she has trouble brushing her hair and buckling her shoes. Her doctor said she cannot lift more than 20 pounds, repeatedly flex her wrists and elbows or keep her arms extended at shoulder height for long periods.
Williams' problems began within months of taking an assembly line job at the Georgetown, Ky., manufacturing plant in 1990, she claimed. She developed carpal tunnel syndrome in her wrists and tendinitis in her hands and arms soon after beginning work at the plant.
She was transferred to another job inspecting cars, which eased the problem. But her work duties later were expanded to include another job in the paint inspection section requiring her to wipe down passing cars at a rate of one car per minute.
Her problems reappeared, along with tendinitis in her shoulders and neck. Williams asked to be reassigned to her former job in the paint inspection section. When Toyota refused to take away the expanded duties, she sued.
At oral argument in November, the justices focused on how employers and courts should classify people who may be unable to do some tasks, but are perfectly capable of doing others.
"Don't you have to look at both what they can do and what they can't do?" O'Connor asked Williams' lawyer then.
The U.S. Chamber of Commerce and other business groups backed Toyota. Several civil rights, legal and labor interests supported Williams.
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