toThe threatening caller, a woman miffed about her tax increase, called the Broward County property appraiser to say "you now have anthrax spores." She sounded credible because she referred to "infectious agents" stored at the National Institutes of Health.

The message, left by Michelle Ledgister in 2005, triggered a call to the Broward Sheriff's Office, then to the FBI's Joint Terrorism Task Force, and finally to the NIH — where Ledgister indeed worked. "Putting it all together, we thought we had the real deal here," said Warren Emerson, a BSO detective with the task force, known as the JTTF.

But the JTTF in South Florida — one of 56 nationwide linked to the FBI's counterterrorism center in Washington — soon discovered that Ledgister had no access to the lethal anthrax. It was a false alarm, but it highlighted the terrorism task force's mission: chase possible threats to national security by combining the vast power of the FBI with the street smarts of local cops.

It's a partnership born of necessity, made more urgent since the Sept. 11 terrorist attacks jolted the country and exposed law enforcement's failure to share evidence that might have stopped the plot.

"The perception before 9/11 was that terrorism didn't happen here, but it did happen," said J. Chris Klettheimer, acting supervisor of the JTTF in South Florida. Through the task force, "now everybody's dialed in."

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