zimmerman. the speech scientists said with three seconds of uninterrupted screaming on the 911 call, there is no way to know for sure. >> we determined that screaming was not normal. it was by someone who was facing probably imminent threat of death or something. very difficult to analyze. >> reporter: still, the neighbor who made the 911 call told "ac 360" she believes it was trayvon martin screaming for help that night. >> i definitely could tell it was a younger youthful voice than it was the deep voice that i heard when they were arguing, and i heard them outside my window. >> reporter: trayvon's mother also told us she has no doubt the screams came from her son. >> people can say anything they want to. i just personally don't believe it. i know that it was my son that was crying out for help. >> reporter: george zimmerman's father testified the screams belong to his son. >> were you able to identify