In closing arguments, prosecution appeals to science while defense decries 'tunnel vision'
Prosecution attempts to place Barrett near murder scene with testimony about distinctive article of clothing
Trial set to begin in the morning with opening statements and testimony from the murdered girl's mother
Current U.S. Attorney, who represented former defendant Womack, may be called as witness
Hearings unveil a previously unknown possible motive for killer -- but a ruling today means it may not come up in court