prosecutors were pretty sure ashlea's murder was a thrill kill planned by a sadistic young woman who thought she was smarter than everyone else. but tiny, meek, carter cervantez admitted none of that. she still had a plan, concocted all by herself, to explain why she, too, was a victim. coming up -- a vicious killer? >> reporter: you wanted to see the death penalty? >> death penalty was what i wanted. >> or a young woman forced into a life of crime? >> were you in pain? >> yes. i was screaming. >> when "dateline" continues. here, safe driving saves more than just your cargo. ♪ ♪ safe driving saves you 40% with drivewise. ♪ ♪