Philip Chism is led into Salem Superior Court for a June hearing. He is accused of raping and killing Colleen Ritzer, his Danvers High School math teacher. (June 30, 2015 photo)

SALEM, Mass. — A jury convicted Massachusetts teenager Philip Chism Tuesday of raping and murdering his algebra teacher.

Chism, 16, was found guilty of first-degree murder, aggravated rape, and armed robbery in the 2013 dead of math teacher, Colleen Ritzer, 24, of Andover, Massachusetts. 

He was tried as an adult. 

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 defense said Chism was hearing voices and in the throes of a psychotic episode when he killed Ritzer.

The Associated Press contributed to this story.