across the harbor in staten island, police had determined the fate of anna scivetti one year after her disappearance. >> our investigative efforts on the case has led us to the conclusion that she's been the victim of a homicide. >> but still no arrest. her sister angel remains defiant and focused on charlie chorman. >> i spent a whole year researching criminals and domestic violence because i wanted to see who i was dealing with. >> angel said charlie's violent nature became more apparent as she spoke to more of anna's friends. >> i saw him grab her, throw her up against the wall, choke her. put his arms on her neck and left marks where his hands had been. >> as part of his course on investigations, gil alba helps