FEAR INC. -- A TIMES INVESTIGATION - Selling the threat of bioterrorism - A scientist defected, warned of epidemics, helped shape policy and sought to profit.

As a doctor of microbiology, a physician and a colonel in the Red Army, he helped lead the Soviet effort. He told U.S. intelligence agencies that the Soviets had devoted at least 30,000 scientists, working at dozens of sites, to develop bioweapons, despite a 1972 international ban on such work.

He said that emigrating Russian scientists and others posed imminent threats. After the breakup of the Soviet Union, he said, several specialists went to Iraq and North Korea. Both countries, he said, may have obtained anthrax and smallpox. The transfer of smallpox would be especially ominous because the Russians, he said, had sought to genetically modify the virus, posing lethal risk even to those who had been vaccinated.

His expertise, combined with his dire pronouncements, solidified his cachet in Washington. He simplified his name to Ken Alibek, became a familiar figure on Capitol Hill, and emerged as one of the most important voices in U.S. decisions to spend billions of dollars to counter anthrax, smallpox and other potential bioterrorism agents.

"It was Alibek's revelations, when he defected, that really provided the first information about the scope" of both the Soviet program and the possible proliferation to Iran and Iraq, said Dr. Thomas Monath, who was a top biodefense specialist for the U.S. Army.

Monath, who later led a group of experts that advised the Central Intelligence Agency on ways to counter biological attacks, said Alibek's information resonated at high levels of the U.S. government and was "amplified by 9/11."

"I think he influenced many people who were in position to make some decisions about response," Monath said, adding, "Concern about smallpox, in particular, was driven by Alibek."

Dr. Kenneth W. Bernard, who served President Bush as a special assistant for biodefense, agreed, saying that Alibek "had a substantial and profound effect."

Having raised the prospect that Iraq had acquired the ability to wield smallpox or anthrax, Alibek also was outspoken as the U.S. went to war in early 2003, saying there was "no doubt" that Saddam Hussein had weapons of mass destruction.

Officials still value his seminal depictions of the Soviet program. But recent events have propelled questions about Alibek's reliability: