Shawn Carr has been charged with third degree murder and involuntary manslaughter.  According to the criminal complaint, a witness told police that he had seen Carr inject Knapp in the arm with what police call a lethal dose of heroin.  Police say Carr drove Knapp to Clarion County and witnesses tell them Carr put Knapp in the driver seat with a syringe in her lap to make it look like she overdosed there.  Charges filed in connection with a woman's disappearance from Jefferson County.  Devan Knapp's body was found mid January in Clarion County about a half an hour away from where she lived.