Suicide doctor Jack Kevorkian lost a Supreme Court bid Monday to revive his libel suit against medical groups that called him a criminal and a "reckless instrument of death." 

The court, without comment, turned down Kevorkian's argument that the statements were false and were not constitutionally protected free speech. 

Kevorkian says he has attended more than 130 suicides. He is serving a 10- to 25-year prison sentence in Michigan for second-degree murder after being convicted in the 1998 death of a terminally ill man whose death he videotaped. 

Kevorkian sued the American Medical Association and the Michigan State Medical Society in 1996 over statements on AMA stationery, also disseminated by the state medical group, that he was a "reckless instrument of death" who "poses a great threat to the public" and that he engaged in "criminal practices." 

He also cited an AMA news release that accused Kevorkian of "continued killings," as well as a news article that quoted an AMA official as calling him a killer. 

A state judge refused the medical groups' request to dismiss the case, but an appeals court reversed and threw out the case in August 1999. 

The court said lawsuits should be dismissed in cases where "an allegedly libelous statement cannot realistically cause impairment of reputation because the person's reputation is already so low." 

"We find that, as to the issue of assisted suicide, (Kevorkian) is virtually libel proof," the appeals court said, adding that the statements were "protected opinion." 

In the appeal acted on Monday, Kevorkian's lawyers said he had not been convicted of a crime at the time the statements were made. 

"There is no constitutional protection for false statements or accusations of criminal conduct or wrongdoing," his lawyers said. "Lies cannot be cloaked by the shield of 'opinion' when published with knowledge of falsity." 

The case is Kevorkian v. American Medical Association, 00-1361.