U.S. District Court Judge Denise J. Casper rejected demands by Bulger's attorneys for the name of the informant, saying the information was not relevant to the charges for which Bulger is on trial, The Boston Globe reported.
Information from the informant allowed the federal government to seize Bulger's share of $14.3 million in a 1991 Mass Millions lottery game. He was to receive $119,000 a year for 20 years.
Defense attorneys had argued for the informant's name to be released to them, saying they needed the information to undermine the testimony of Kevin Weeks, a former close fiend of Bulger's who is scheduled to testify for the prosecution at Bulger's upcoming racketeering trial.
Casper ruled "there is no suggestion that the CI [confidential informant] played any role in the criminal conduct charged here."
Bulger is facing 48 charges including 19 murders, extortion and money laundering. Not one of them, the judge said, deals with the defendant's activity surrounding the lottery ticket.
"The key consideration is not that there is no pending investigation or law enforcement interest remaining in the underlying matter," Casper said, "but that the qualified privilege presumes confidentially unless the burden to disclose such information is met. "