A Southwest Missouri man says he`s guilty of causing the death of his son. 19-year-old Christopher Lee Smith entered that plea in Jasper County court yesterday. Smith was charged with second-degree murder for the December 29th, 2000 death of 7-week old Brandon Smith. Investigators say the young boy was found dead in the family home in Waco, Missouri. They say the cause of death was trauma to the baby`s head. Smith will be back in court for his formal sentencing on January 7th.