Updated

Prosecutors are asking a judge to sentence a Massachusetts teenager who raped and killed his math teacher to at least 50 years in prison.

Seventeen-year-old Philip Chism will be sentenced Friday in the 2013 killing of Danvers High School teacher Colleen Ritzer. He was 14 when he killed her.

Essex District Attorney Jonathan Blodgett's office filed a memo in court Thursday asking that Chism be sentenced to life in prison on the murder charge, with parole eligibility after 25 years. Prosecutors also asked for a life sentence with parole eligibility after 25 years on a charge of aggravated rape. They want those sentences served consecutively.

Chism's attorney has asked that his client be given concurrent sentences and serve 26 years in prison.

Jurors rejected an insanity defense.