Homicide - Cigarette Butt - S4.E7

Joe and Bill investigate a dead body found in a rundown apartment building. A half eaten peanut butter sandwich and a knife are found at the scene of the crime. A neighbor says that he saw a man and woman running out of the apartment. The man and woman come back and tell Joe and Bill that it was self defense. Joe looks for evidence that will prove or disproves the alibi.