Boy, then 14, raped and murdered math teacher at school, wheeling her body out in a bin

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Massachusetts high school teacher Colleen Ritzer (left) in a family photo. On the right, her student Philip Chism is shown wheeling her body through the school in a bin, after he raped and murdered her. Photos: CNN/AP

Published: 8:30am, 16 Dec 2015Updated: 9:12am, 16 Dec 2015

A teenager has been convicted of raping and murdering his math teacher at a high school in the state of Massachusetts when he was 14.

Philip Chism, now 16, followed his 9th grade algebra teacher, Colleen Ritzer, into a school bathroom, where he strangled her, stabbed her at least 16 times and raped her. He later wheeled her body out of the school in a garbage bin.

Chism was convicted of a raping Ritzer inside the bathroom but was acquitted of a second rape, committed with a tree branch in woods near the school where Chism dumped her body. He was convicted of armed robbery for stealing Ritzer’s credit cards and her underwear.

Chism stared straight ahead and did not have any visible reaction as the verdicts were being read in Salem Superior Court.

Philip Chism appears in Salem Superior Court on Monday during closing arguments in his trial. Photo: AP

During his trial, his lawyer admitted Chism killed Ritzer, but said he was suffering from severe mental illness and was not criminally responsible for his actions. A psychiatrist who testified for the defence said Chism was hearing voices and in the throes of a psychotic episode when he killed Ritzer.

Ritzer, 24, was a popular teacher at Danvers High School, about 40km north of Boston, doing her dream job, teaching math, Assistant District Attorney Kate MacDougall told jurors in her opening statement.