nelson villavicenzio and his wife were just outside while the murder occurred. had they stopped in to say hello to sarah, they, too, might have been victims. in october of 2006, kosoul was convicted of capital murder, and sentenced to death. >> people will kill for the most trivial of reasons. reasons that no rational person would ever imagine. >> what the science did in this case is it made that defense attorney get up in his opening sentence and say my client was guilty and this was a robbery gone bad. he would not have said that if we hadn't had the physical evidence we had in this case. >> this case turned out to be the perfect marriage of good police work, excellent science, and prosecutorial expertise. it was the perfect blend of all three of those things coming together, to where we got the case from the day sarah was murdered until he was convicted and sentenced.