TALLAHASSEE - Burson Augustin was arrested last June, charged with plotting to blow up the Sears Tower and conspiring to help al-Qaida blow up federal buildings in major cities across the country.

Augustin and two co-defendants from Miami's Liberty City neighborhood also had something else in common: the state of Florida had issued them private security guard licenses.

Florida has some of the most stringent licensing background checks in the country, officials and private security company executives said. But the arrests on terrorism charges - which have not been proven in court - demonstrate that even a stringent system can't be foolproof. Without previous arrests or inclusion on a terrorism watch list, denying licenses to people like Augustin would require the ability to see the future.

"(Augustin) met all the criteria outlined by the state," said Eddie Sorrells, chief operating officer and general counsel for DSI Security Services, which employed Augustin for four months in 2005 when he resigned. "He had licensing in good standing, federal and state checks. To our knowledge, he had a clean criminal record."

Unlike some states that have virtually no regulation of the private security industry, Florida has set procedures that involve both state and national checks. And security companies often have additional checks they make applicants go through.

The Department of Agriculture and Consumer Services, which oversees the licensing program, forwards applicants' names and fingerprints to the Florida Department of Law Enforcement, which runs them through a state database. The name and fingerprints are then run through the National Crime Information Center, a database that contains criminal intelligence information such as terrorism watch lists.

If a search turns up an arrest record, that record is sent back to licensing officials, who investigate what happened and whether there was a conviction, said Division of Licensing Director Buddy Bevis.