Haunting footage of a maths teacher's final moments before she was raped and killed show her alleged murderer following her down a school corridor.
The body of Colleen Ritzer, 24, was found dumped in woods behind Danvers High School in Massachusetts in October 2013.
Student Philip Chism, 16, is standing trial charged with rape, murder and robbery.
He is accused of twice sexually assaulting his maths teacher before slashing her throat with a box cutter.
He is later said to have bought a Wendy's meal with the dead teacher's credit card.






