A Massachusetts teenager was convicted on Tuesday of killing his high school math teacher after following her into a bathroom and brutally strangling, stabbing and raping her.

Philip Chism, now 16, was 14 and in ninth grade when he followed algebra teacher, Colleen Ritzer, 24, stabbed her at least 16 times before taking her body away in a recycling bin.

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 at Danvers High School, north of Boston.

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Philip Chism (pictured in court on Monday), was convicted on Tuesday of raping and killing his high school math teacher, 24-year-old Coleen Ritzer

 

 

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Ritzer (pictured left and right), 24, was a popular teacher at Danvers High School, about 25 miles north of Boston

A psychiatrist who testified for the defense said Chism was listening to commands from voices in his head and in the throes of a psychotic episode when he killed Ritzer in 2013.

Witness Dr Richard Dudley, who met with Chism seven times during the time before his trial, said during his testimony that Chism at the time of the killing believed he was a ninja.

The defendant, who was tried as an adult, was also convicted of robbery for stealing the teacher's credit cards, one of which was used at the movies, and her underwear.

Chism was acquitted of a second rape, which was allegedly committed with a tree branch in the woods where he put Ritzer's body. 

On October 22, 2013, Ritzer asked Chism to stay after school, and a witness said she tried to talk to the recent arrival in Massachusetts about how his new community compared with his old town of Clarksville, Tennessee.

Another student said Chism became visibly upset and Ritzer changed the subject before eventually heading out in the hallway to go to the bathroom.

Surveillance footage from the school shows Chism poking his head out of her classroom and looking down the hall after she had gone.

 

 

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Surveillance footage at the school captured Chism during his movements in the hallway where he followed Ritzer to the bathroom where he strangled, stabbed and raped her 

 

 

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Video showed Chism wheeling a large recycling bin carrying Ritzer's remains. During his trial, his lawyer admitted Chism killed Ritzer, but said he was suffering from severe mental illness

 

 

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Chism was acquitted of a second rape allegedly committed with a tree branch. Above, footage shows Ritzer taking the recycling bin to the woods

He then goes back into the classroom, but comes right back out with his hood on. 

Chism is then shown putting on a pair of gloves as he walks into the bathroom, emerging minutes later carrying the black pants Ritzer was wearing. 

A bloody box cutter, mask, gloves and a hooded sweatshirt were later found in his backpack by police who found Chism walking beside a highway in neighboring Topsfield.

The items brought to school that day were used to make the case that the ninth grader premeditated the attack and 'knew right from wrong'.

Chism's lawyers had said he should be acquitted of the rape in the woods, arguing Ritzer was already dead by then. 

Prosecutors, however, had said Chism did not deliver the fatal stab wounds to her neck until he brought her outside. 

When Ritzer's body was found she was nude from the waist down, covered in leaves,' MacDougall said, according to the Boston Globe. 

A note near the body said, 'I hate you all'. 

Defense attorney Denise Regan said that her client's family has a history of mental illness and that he likely suffered from it from an early age.

A doctor who testified for the state that Chism was not psychotic and hsi symptoms were inconsistent.

The jury deliberated for more than ten hours over two days before delivering its verdict. 

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

He now faces  life in prison on the first-degree murder charge. 

As a juvenile, he cannot receive a life sentence without parole, which is automatic for normal adult offenders.

The first opportunity for parole would first come after he serves 15 to 25 years. 

His mother declined to talk to reporters as she left the courthouse.

Standing later with the district attorney that prosecuted the case, Ritzer's parents said the verdicts mark a new phase in their lives in which they hope to honor their 24-year-old daughter's legacy.

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

'There remains a tremendous absence in our lives, one that sadly can never be replaced.'

The family, he added, will still be reminded of the crimes as Chism appeals the case and is eligible for parole at some point. 

'We will carry on and do our very best to find the good in every day,' said Peggie Ritzer, the victim's mother.

Chism's lawyers are also expected in court in Boston on Wednesday as he faces separate charges of attempted murder and assault and battery with a dangerous weapon after he allegedly attacked a state Department of Youth Services worker in June 2014 while awaiting trial.

Prosecutors in that case say Chism had been in custody at a youth detention facility in Boston when he followed a female worker into a locker room. 

They say he choked and beat her before other workers intervened. The unnamed worker suffered injuries to her face, jaw, neck and back.