(CNN) -- Trayvon Martin's parents will ask the U.S. Justice Department to review a local Florida prosecutor's interactions with police investigating the teen's shooting death, the family's lawyer said. The Justice Department launched an investigation into Martin's death on March 19, but the family is now asking it to look for possible interference by State's Attorney Norm Wolfinger's office with Sanford, Florida, Police Detective Chris Serino, attorney Ben Crump said. The Martin family will send a formal request to the Justice Department Monday, Crump told CNN Sunday.