BOSTON (AP) — Prosecutors are trying to discredit a former FBI supervisor who claims he tried to end the FBI's corrupt relationship with reputed mobster James "Whitey" Bulger.

Robert Fitzpatrick, testified that he tried to convince the FBI to terminate Bulger as an informant after Bulger was uncooperative and didn't appear to be helping the bureau's mission to gather information on the Mafia.

Fitzpatrick became the first defense witness at Bulger's racketeering trial when he took the stand Monday.

During cross-examination Tuesday, a prosecutor suggested that Fitzpatrick had exaggerated the extent of his effort to terminate Bulger as an informant.

Fitzpatrick said higher-ups in Boston and Washington felt Bulger "was going to bring down the Mafia."

Earlier Tuesday Judge Denise Casper rejected a bid by Bulger to sequester jurors while they deliberate.

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