A Massachusetts jury on Tuesday found 16-year-old Philip Chism guilty of raping and murdering his math teacher when he was 14.
Chism was charged with first-degree murder and two counts of aggravated rape in the brutal assault and murder of his 24-year-old math teacher at Danvers High School in 2013.
His defense team had argued he was not mentally sound at the time of the killing, but the Essex Superior Court jury on Tuesday found him guilty of first-degree murder and one count of aggravated assault.
During the jury's verdict, Chism appeared stoic. His mother, Diana Chism, doubled over in tears.
Chism faces life in prison with the possibility of parole after serving 15 to 25 years.
Tuesday's verdict ends two weeks of disturbing evidence that included surveillance footage that documented nearly every step of the assault and murder.
On Oct. 22, 2013, Chism lingered behind in Ritzer's math class after school when she typically led additional tutoring sessions for students who needed extra help.
Ritzer, who was on a committee of teachers organized to help freshman students adjust to high school, asked Chism questions about how he felt about Danvers and his former hometown of Clarksville, Tennessee.
Autumn Ciani, who was the only other student in the classroom that day, testified that Chism appeared agitated by Ritzer and she eventually left him alone.
Video footage shows Ritzer walking to the bathroom with Chism just steps behind her.
He followed her inside where he slashed her legs, slit her throat with a box cutter, and raped her inside a stall. The cuts were so deep they hit her vertebrae, prosecutors said.
A cleaning worker who testified during the trial described the blood splashed across the walls and floor as a "slaughterhouse."
Surveillance footage shown by the prosecution shows Chism fetched a recycling barrel, placed her body in it, and rolled it towards woods nearby the school. He dumped her body and then violated her corpse with a tree branch, before leaving a note in blue ink on her body that read “I hate you all.”
Additional footage from a nearby movie theater showed Chism buying a movie ticket with Ritzer's credit card.
Chism's mother reported him missing when he didn't come home that evening. Police found Chism wandering the outskirts of town on a desolate road. He appeared distant and "strange," according to police testimony.
An officer asked if he had anything on him that could harm them. He said yes and opened a wallet holding the bloodied box cutter.
“Whose blood is this?” asked the officer.
“The girl’s,” he said.
“Where is the girl?”
“In the woods.”
“If we find her, can we help her?”
“No.”
Chism's defense team argued that Chism's actions were a part of a psychotic episode. Much of the testimony and evidence focused on the mental health of Chism at the time of the killing.
Dr. Richard Dudley Jr., a psychiatrist who testified for the defense, diagnosed Chism with psychosis just this year, arguing the teen could not be held responsible for his actions because he was suffering from a psychosis that included auditory hallucinations compelling him to harm Ritzer.
He could hear imaginary voices "as clearly as he could hear my voice,” the psychiatrist said.
Chism's maternal grandfather Eduardo Barbieri said that the family has a history of mental illness. He said Chism's aunt suffered from mental illness and cycled in and out of mental health facilities over several years. Chism's grandmother was put through shock therapy after a mental breakdown in 1975, he said.
However, jurors ultimately sided with the prosecution's argument that Chism had murdered his teacher with premeditation. They argued that Chism came prepared with a mask and box cutter to carry out the murder.
The gruesome assault on Ritzer shocked the small town of just over 26,000 people. Ciani described Ritzer in court as a teacher beloved by all students at Danvers High School.
“She was a great person,” she said.
Ciani said Ritzer made math fun and that she often couldn't wait to attend class.
The second day of the trial, Ritzer's mother, Peggie, wore a pink sweater when she took the witness stand. Pink was Colleen's favorite color.
“She wanted to be a teacher from the time she was in preschool,” Peggie Ritzer said of her daughter, whom she described as her best friend. “As she got older, she excelled in math, so she wanted to teach math.”
A pre-sentencing conference for Chism is scheduled for Dec. 22.