Federal prosecutors charged Nicodemo Scarfo with racketeering, illegal gambling and loan sharking in 2000, and described him as being a member of the Mafia. The case took on broader significance when the government introduced evidence gained from secretly installing a keystroke-logging tool on Scarfo's computer in order to crack the PGP encryption on one of his files.
Defence lawyers tried to suppress the evidence as unconstitutional, and requested details about the workings of the keystroke-logging tool in a bid to show that it violated the US Constitution's Fourth Amendment protection against unreasonable search and seizure.
The prosecution, however, successfully invoked the Classified Information Protection Act, asserting that the government has a compelling national security interest in keeping the technical details of the system from public view.
The guilty plea means that privacy advocates will have to wait for another case to get a higher court hearing the constitutional challenge to the government's use of the technology, said David Sobel, general counsel to the US-based watchdog, the Electronic Privacy Information Center.
Sobel said: "We know that Carnivore [the FBI's controversial e-mail surveillance tool] has been in use for two years now, and there hasn't been a case where evidence gathered with it has been used in court."