US teen raped and killed maths teacher

Chism did not react when the guilty verdicts were read

A teenager in the US state of Massachusetts has been convicted of raping and killing his high school maths teacher.

Philip Chism, 16, followed teacher Collean Ritzer into a school toilet where he strangled her, stabbed her 16 times and raped her two years ago.

He was acquitted of a second rape, in which he used a tree branch against her in woodland where he dumped her body.

Chism's defence team has claimed he is mentally ill and will appeal.

They do not deny that he killed the teacher but insist he cannot be held responsible for his actions.

A psychiatrist testified on behalf of the defence during the trial and said the teenager was hearing voices and in the midst of a psychotic event when he committed the crimes.

The teenager did not have any visible reaction as the verdicts were read in a court in the city of Salem, and his family has refused to speak to reporters.

The victim's family, however, spoke of their enduring pain in light of the verdict.

"This guilty verdict, while the beginning of justice for Colleen, is certainly no cause for celebrations as there can never be true justice for the crime committed," the victim's father, Thomas Ritzer, said.

The victim's family was emotional when the verdict was read

On surveillance footage presented in the trial, Chism is seen following the teacher to the bathroom, putting on gloves and leaving holding the trousers that Ritzer was wearing.

He was acquitted of a second rape charge that allegedly happened in the woods, after defence lawyers argued that the teacher was already dead.

Chism was tried as an adult, and could face life in prison for the first-degree murder conviction. However, because he is a juvenile he could be eligible for parole. Judge David Lowy says he will discuss sentencing at a hearing next week.

Separately the teen is facing charges of assault on a youth services worker. He allegedly choked and beat the worker while in a youth detention centre in Boston.

Jurors were shown a box cutter used in the murder during the trial