WASHINGTON -- The informant who wore a wire and helped build the case against four men charged with plotting to blow up Kennedy Airport is a longtime cocaine dealer who cooperated with investigators after being convicted of possession of about $2 million worth of cocaine in 2003, according to court documents posted on thesmokinggun.com.

The 36-year-old man is described in the documents as a onetime member of a violent drug gang first convicted in 1996 of selling cocaine and crack in Manhattan, Brooklyn and Queens and conspiring to murder a rival drug kingpin. The rival survived the attempted hit, according to the federal complaint in the drug trafficking and racketeering case.

Police and prosecutors declined to confirm or deny the identification of the man they have referred to only as the "Source," who also had been pictured and named in Caribbean media. But they publicly acknowledged in the terror plot indictment that the informant is a twice-convicted drug trafficker who wore a wire in return for undisclosed pay and the promise of a reduced or commuted prison sentence on a 2003 drug trafficking conviction.

"We're concerned about the safety of the Source and are taking measures to safeguard him," said FBI spokesman James Margolin. "I guess The Smoking Gun made an editorial judgment that our concerns were outweighed by the public's right to know, or commerce or whatever."

The informant is key to the case against the alleged terror plotters. At the behest of police, he insinuated himself into the confidence of alleged mastermind Russell Defreitas, 63, a former airport cargo worker and three others charged in the plot.

During the course of about a year, the informant drove Defreitas to Kennedy Airport to conduct repeated surveillance and traveled with him to the Caribbean to try to win support from an Islamist group based in Trinidad to carry out the plot.

The use of a convicted felon to crack an alleged terror plot is not unusual. Police are increasingly turning to informants or undercover agents who pose as Islamist radicals to infiltrate suspected cells. Despite the credibility problems of witnesses who are convicted criminals, prosecutors say that jurors are often convinced by tape recordings.

In this case, prosecutors contend the information provided by the informant was corroborated by tape recordings, e-mails, financial documents and surveillance.

The court papers posted on thesmokinggun.com suggest the Source in the JFK terror plot was actually a practiced informant. He spent about six years in jail on his first, 1996 conviction -- far less than the 26 to 34 years called for in federal sentencing guidelines. Judge Loretta Preska indicates in a 1996 document that he received consideration because of his "substantial assistance" to the government.

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