weeks in, detective julissa trapp seemed stuck. i think she got a little frustrated, and got a little desperate, and came up with the idea of using the computer database. reporter: that is the computer database of sex offenders. if they had a serial killer on their hands, there was at least a chance he d already run afoul of the law at some point. it was a bit like just poking a finger into the haystack frankly and hoping to encounter a needle. but worth a try. so trapp called this woman. sexual assault detective laura lomeli. all sex offenders on parole, they will have an anklet, a gps monitor. reporter: trapp asked lomeli, were any of those gps monitors here, where jarrae placed her last phone call, or here, where she wound up in a dumpster? and if you find the same guy at both locations, you re getting somewhere? uh-huh. reporter: lomeli ran the search. and what were the chances? she got a hit. in both locations. she called detective trapp.
seemed stuck. i think she got a little frustrated and got a little desperate, and came up with the idea of using the computer database. reporter: that is the computer database of sex offenders. if they had a serial killer on their hands, there was at least a chance he d already run afoul of the law at some point. it was a bit like just poking a finger into the haystack frankly and hoping to encounter a needle. but worth a try. so trapp called this woman. sexual assault detective laura lomeli. all sex offenders on parole, they will have an anklet, a gps monitor. reporter: trapp asked lomeli, were any of those gps monitors here, where jarrae placed her last phone call, or here, where she wound up in a dumpster? and if you find the same guy at both locations, you re getting somewhere? uh-huh. reporter: lomeli ran the search and what were the chances she got a hit.