there. >> it's four people, not just michelle and her husband and devon. it was also keary was involved. and keary was the spark plug, if you will. >> in tracing devon guzman's last known movements, a witness told police he saw devon guzman at michelle and brandon's home on the night of her murder. >> i woke up because there was some noise outside that i realized was an argument. the woman i now know to be devon was standing on the doorstep on the house in back of me with two people inside the house, the three of them arguing. i looked at the clock. it was 12:35. >> detectives sprayed the inside of the couple's home with fluorescein, which is like luminol in that it glows when it comes into contact with red blood cells. they found nothing. >> we should be able to detect blood all over the place if this is where her throat was cut, and