By Scott Malone
BOSTON (Reuters) - A federal judge has rejected accused mobster James "Whitey" Bulger's plan to argue that he cannot be prosecuted for 19 murders because of an immunity agreement worked out with a now-deceased prosecutor.
In a court filing made public on Thursday, District Court Judge Denise Casper said lawyers for Bulger could not make the case at trial that he had immunity from prosecution.
Casper was appointed to hear the Bulger case in March, after a federal appeals court removed Judge Richard Stearns because of his history as a federal prosecutor.
Casper upheld Stearns' ruling that a judge should decide whether Bulger had immunity before the jury trial and that no valid immunity agreement would have allowed murder.
"Although Bulger contends that 'Judge Stearns' rulings on these issues were almost entirely adverse to the defendant,' ... an adverse ruling does not mean that the rulings were wrongly decided or were 'tinged with bias' as Bulger contends," Casper wrote in a 31-page order.
Bulger's lawyers have said little about his immunity agreement, which they said was reached with former Assistant U.S. Attorney Jeremiah O'Sullivan, who died in 2009. They contended that Bulger was never a government informant, but have not said why prosecutors would have offered immunity if not in exchange for information.
The 83-year-old accused mobster is accused of committing or ordering 19 murders in the 1970s and 80s as leader of Boston's "Winter Hill" gang. He has pleaded not guilty to all charges and faces the possibility of life in prison if convicted in a trial set to begin next month.
(Reporting by Scott Malone; Editing by Doina Chiacu)