"well, surely, any day now. any day now." >> reporter: investigators had their suspicions as well and they were trying to build a case against smoot. he was the last to see her alive. they had an allegedly violent relationship. he had lied to investigators. but so far they had found no physical evidence tying him to the crime. you were able to search shawn smoot's apartment? >> we were. >> reporter: do you find anything? >> we find an empty box -- that once contained a firearm with some -- ammunition. >> reporter: no gun? >> no gun. >> reporter: the box was for a .32 caliber pistol. the same caliber as the murder weapon. and the ammo? >> it was the same -- style of ammunition -- that was found at the murder scene. >> reporter: but without the actual gun itself, the circumstantial case wasn't strong enough to charge smoot with murder. then, the crime lab released its ballistics report showing that marks on shell casings from the