A special court has sentenced 13 people to life imprisonment in a 14-year-old triple murder case in Madhya Pradesh's Betul district. Special judge Rakesh Mohan Pradhan awarded life sentence to the accused on Wednesday evening, a prosecution official said. As many as 17 people were named accused for the killings that took place on September 9, 2006, senior government advocate Shashikant Nagle said.