The director of the state crime lab in Massachusetts has been chosen to lead the troubled crime lab in Connecticut. The appointment of Guy Vallaro as director of the state Forensic Science Laboratory was announced Monday. The Connecticut lab has struggled with a huge case backlog and other problems identified in US Justice Department audits. It regained its professional accreditation earlier this year. The crime lab currently led by Vallaro is separate from the Massachusetts Department of Health laboratory where a chemist is accused of faking drug test results.