cold case unit at the orange county da's office to a guy named larry montgomery. 0 years working homicide. larry put away his share of bad guys and not usually by knocking on doors, instead larry works by looking closely at the evidence. he does not work fast. in fact, larry is meticulously slow and that was just what this cold case needed. >> reporter: was there anything in the original investigation that struck you as something you needed to re-examine? >> everything. >> reporter: everything that led police into that wall trying to decide between two suspects. >> i am concerned about this girl and she's missing. >> reporter: marty, lynsie's older friend who kept their relationship a secret and chris. the last person known to have seen lynsie when he dropped her off at that corner. >> reporter: any idea which of those two are a likely suspect? >> no, i don't know until i got into the details. >> reporter: you got reputation of god's in the details. >> reporter: guilty or innocent? was it marty or chris? larry considered another possibility. could it have been rand