Two US parents accused of killing their daughter by making her drink more than two litres of soft drink and water in a cruel and bizarre act of punishment have pleaded not guilty to her murder. Father Randall Lee Vaughn, 41, and stepmother Mary Vaughn, 58, face charges of murder and child abuse following a two-year investigation into the death of 5-year-old Alexa Linboon. A discoloured and unresponsive Alexa Linboon was taken to an emergency room in the state of Tennessee on January 1, 2012, the Los Angeles Times reports. Alexa experienced seizures and was legally declared brain dead. She...