>> karen hamm-samuel. >> reporter: and how did they know who she was? m was somebody i had already profiled as a person who came up frequently on diana's call records. she was a high frequency caller. >> reporter: so you got a friend of diana's buying the disposable phone that called peggy just before she was killed? >> yes. that was a big moment. >> reporter: now they knew who had bought the phone. the next step was to figure out who had turned the tracfone on. tracfones need to be activated using another phone to call an 800 number. after three weeks, detective cole-hatchard finally persuaded a tracfone manager to give him this piece of paper. >> he had circled a phone number. and it was the number that called to activate that tracfone. >> reporter: whose number was that? >> andrea benson. >> reporter: had that name surfaced before? >> yes, absolutely. >> all over diana's phone records. >> reporter: she was one of those people who had popped into diana's life when diana was in d.c. and benson had a rap sheet. so what's going on here? how many people ar