BOSTON (AP) — Prosecutors say a judge should decide Boston mobster James ‘‘Whitey’’ Bulger’s claim that he was granted immunity for being an FBI informant.

Bulger’s lawyers say a jury should determine the merits of his argument he was granted immunity by a former U.S. attorney who later died.

Prosecutors said in a filing Wednesday 83-year-old Bulger weakened his argument by saying in a recorded 2012 jailhouse conversation with one of his brothers that he wasn’t an informant. The Boston Globe reports (http://bo.st/YEPIU9) the court filing quotes Bulger as saying, ‘‘I bought (expletive) information, I didn’t sell it.’’

FBI records in other court filings say Bulger was an FBI informant from 1975 to 1990, and fled when he was tipped by his FBI handler before a 1995 indictment.

Bulger, charged in connection with 19 slayings, was captured in California in 2011.

___