The lawyer for Maine dentist Randon Bragdon argued that Bragdon did not illegally discriminate against an HIV-infected woman by refusing to treat her at his office.
The patient, Sidney Abbott, suffers no AIDS symptoms and therefore is not protected by the Americans With Disabilities Act, said attorney John McCarthy.
But Abbott's lawyer said lower courts correctly found that Bragdon violated the law, which bars discrimination against the disabled in jobs, housing and public accommodations.
The law responsible for such aids as wheelchair ramps at countless public places says people are disabled if they have a physical or mental impairment that "substantially limits one or more major life activities."
HIV-infected people should always be considered disabled because the contagious and fatal nature of acquired immune deficiency syndrome severely limits their ability to have sex and bear children, said Abbott's attorney, Bennett H. Klein.
Some justices disputed whether HIV infection really creates such a limit.
Justices David H. Souter and Antonin Scalia suggested an HIV-infected person faces a "moral choice" rather than an actual physical limit on his ability to have children.
"I'm not sure that's what the statute is talking about," Souter said.
However, Justice Anthony M. Kennedy said that if a person with highly infectious tuberculosis stays away from other people, "we don't just call it a moral choice."
Someone with bubonic plague would be considered disabled, added Justice Stephen G. Breyer.
Bragdon's lawyer said the disability law aims to protect people whose disabilities affect their "day-to-day independent living and economic self-sufficiency," not HIV-infected people who suffer no symptoms.
The disability-rights law says disabled people can be treated differently if they pose a "direct threat to the health or safety of others."
"Dr. Bragdon believes that when he provides a service in the face of the risk of death he should be allowed to take additional precautions" such as insisting on filling Abbott's cavity at a hospital, McCarthy said.
However, Breyer said that "after 15 years and hundreds of thousands of deaths" from AIDS there appeared to be no documented cases in which a dentist caught the virus from a patient.
"How can we say here that your client exercised reasonable medical judgment?" Breyer asked. McCarthy replied that there were seven possible cases of HIV transmission in dental procedures.
Klein said that unless HIV-infected people have clear protections under the law, many will hide the fact that they carry the virus.
The court never has decided a case involvig an HIV-related issue or the disability-bias law, signed in 1990 by President Bush.
A decision is expected by July. The justices' ruling could provide clues as to whether the law covers other kinds of disabilities, such as cases of epilepsy or diabetes that are controlled by medication.
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