The woman who says she watched her ex-boyfriend rape and strangle 19-year-old Lizzi Marriot will be back on the witness stand. Kathryn McDonough opened her day-long testimony yesterday saying Seth Mazzaglia strangled Lizzi with a rope. McDonough testified she thought Marriott might make a potential sex partner for the Mazzaglia, who was always urging her to recruit young women. She testified she did nothing to help Marriott after Mazzaglia attacked her. Mazzaglia’s attorneys say McDonough killed Marriott.