FBI giving polygraph tests in anthrax probe

Five people died in last fall's anthrax scare, but no arrests have been made.

WASHINGTON (CNN) -- The FBI is asking key scientists involved in the anthrax investigation to take polygraph tests, federal officials said Friday.

The voluntary exams, which gauge the subject's truthfulness, mark authorities latest attempt to find out who mailed anthrax-laced letters to journalists and politicians last fall.

"We haven't ruled anyone out as a suspect," an FBI official said Friday.

As part of its investigation, the FBI is looking into the possibility that the person behind the anthrax attacks may have ties to a government lab.

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Authorities have narrowed the number of facilities believed to be capable of making the deadly spores to about 24 labs. But no charges have been filed against anyone thought to be involved in the anthrax mailings, which killed five people and infected 13 others.

Maj. Gen. John Parker, who retired last month as the commander of the U.S. Army Medical Research Institute of Infectious Diseases at Fort Detrick, Maryland, said the polygraph tests are a routine precaution and began six weeks ago.

"[The FBI] wanted to be reasonably sure as possible that the people who deal with evidence are not part of the problem," Parker said.

Parker said the FBI sought polygraphs only from those scientists and lab technicians who deal directly with anthrax samples and results. He said he did not know how many scientists at Fort Detrick have been asked to take a polygraph or if anyone has refused.

"I think this is a good thing," said Parker.

The Maryland lab is one of the labs capable of producing anthrax spores, and it has shared its anthrax with other labs for research purposes over the years.

Dr. John Ezzell, the scientist who opened the anthrax-laced letter addressed to Sen. Patrick Leahy, D-Vermont, confirmed that he had taken a polygraph test.

"It's a standard procedure for anyone handling evidence," he said.

While polygraphs are often used in criminal investigations, some scientists have questioned their accuracy and dependability.