A U.S. federal court recently ordered the Department of Justice (DOJ) to reveal technology it used to track the computer keystrokes of a suspect, in a case observers say has an impact on privacy in this era of IT surveillance.

In May 1999, agents from the U.S. Federal Bureau of Investigation (FBI) snuck into the New Jersey office of Nicodemo S. Scarfo Jr., according to court records. They planted a device to track the tap of his fingers on his keyboard in a bid to glean the password for an encrypted file, according to the records. The DOJ, working with the FBI, is charging Scarfo with racketeering, illegal gambling and loan sharking as a member of what they call a Mafia crime family.

Agents cracked his Pretty Good Privacy encryption and the evidence became a key part of the FBI’s case. What the court doesn’t know is how the key logger system works. The judge in question called the printout of FBI’s computer keystroke log “gobbledygook” and ordered the government to explain the technology.

The case troubles David Sobel, general counsel for the Electronic Privacy Information Center non-profit advocacy group in Washington, D.C., because of the FBI’s desire to keep the technology secret. “The government is making the case that they can install sophisticated technology on computers and make a national security claim,” to keep it secret, he said. If it became a routinely accepted argument for preventing its disclosure to defendants in court, “it would radically alter our concept of due process and the rights of criminal defendants,” said Sobel.