>> on state's exhibit 1 -- >> reporter: ashlea deenor assisted. from the witness stand detective cedillo helped lay out the case. >> were you able to conduct a search of her apartment and her vehicle, things like that? >> yes, sir. >> and did you find a receipt that proved to be helpful? >> that's correct. >> reporter: a sales receipt showed some odd purchases on carter's credit card. >> she had purchased two shovels. she had purchased a tarp. she had purchased gloves. >> reporter: why was that significant? because of a discovery way out in the texas scrub. a discovery worthy of a horror movie. and the key to finding it was right there on carter and david's cell phones. >> they would text each other longitude and latitude coordinates, and it led us to a remote area near abilene. >> reporter: what was there? >> as soon as we got to where the spot says, "you're there," we look up and there's an actual human grave that's been dug.