Kirkland & Ellis has brought back an alum who led a string of insider trading and securities fraud investigations at the U.S. Attorney’s Office for the Southern District of New York, including the case against Rep. Chris Collins and former law firm partner Walter “Chet” Little.

Robert Allen, 34, joined Kirkland as a partner this month, representing clients in commercial and securities-related cases and in criminal and regulatory investigations. He spent four years in the Southern District office, including more than two years on the Securities and Commodities Fraud Task Force.