BRIAN KELLY, the assistant U.S. attorney in Boston who prosecuted notorious mobster James “Whitey” Bulger, has left his government post and plans to join Nixon Peabody in January.

Kelly, who was also the chief of public corruption and special prosecutions for the U.S. attorney’s office, says that he chose to go to an Am Law 100 firm because “I had just completed Whitey Bulger’s case. It was a transition point, and I decided it was time to do something different.” Bulger was found guilty in August on 31 of 32 counts, including extortion, money laundering, drug dealing, weapons possession and 11 murders.