arrest. >> it was a sad moment, because it's a 16-year-old that did this. it's sad for everybody involved. >> the trial of a teenaged girl killing her parents was a national sensation. >> there were three people in the johnson house that morning when alan and diane were murdered. two of them did not come out. >> at trial, prosecutors presented voluminous forensic and circumstantial evidence to prove that sarah murdered her parents. >> she wanted the big, rich things in her life. she wanted to provide for her boyfriend. they were going to get married. and she asked him, do you want to live in a big, beautiful home? >> with her parents' life insurance and her inheritance, she thought she'd be all set. >> and she could live that happily ever after life that only a 16-year-old probably envisions.