the party. how long did you spend on this? we spent several weeks. that s all we were doing is attempting to identify these people, locate them, interview them, and go through the same vetting process as far as getting a timeline and alibiing them, as everybody else. and we were taking dna samples from every single person we talked to. reporter: at the same time, they asked one of their tech investigators, nick herfordt, to look for clues in jessyka s cell phone. you find all kinds of stuff on people s cell phones, i bet you. oh, my gosh. yeah, absolutely. but what s actually remarkable about this one when you say all kinds of stuff, on this one it was pretty much just one thing on there and it was just pictures of her son. reporter: this kind of stuff. her life just completely revolved around him. reporter: but there were text messages, too. lots of them. and some were pretty interesting. one of the last people she was communicating with, someone was named matt kidder.
that revealed she was home alone. they had discovered that matt s cell phone was at or near jessyka s place for 17 minutes that night. reporter: police tech experts oscar dieguez and nick herfordt. so right now, it s about 11:00, and you re going to see a couple more activations where he s still at work. and right there and then all of a sudden it switches. reporter: and that s at her house. yes, that is directly in the area of the house. reporter: and there was more. the detectives had noticed a crescent-shaped cut on matt s hand. this could have been made by jessyka s thumbnail bending back as she defended herself. the fingernail swabs from her hands. and the blood in the house. he provided his dna sample. during his initial interview. we immediately brought that in.