Former Boston crime boss James "Whitey" Bulger is appealing his conviction last year on racketeering charges that said he played a role in 11 murders.
Bulger's lawyers made the filing Thursday afternoon in a federal appeals court in Boston.
Among their arguments are that Bulger was not allowed to argue that a now-deceased federal prosecutor had given him immunity.
Bulger is now 84 years old. He was the head of Boston's Irish mob and an FBI informant. He was convicted of gangland crimes in the 1970s and '80s and sentenced to life.
His case became an embarrassment for the FBI as corrupt agents accepted bribes and protected him. Bulger was a fugitive for 16 years until his 2011 arrest in California.