SALEM — Philip D. Chism, the teenager who sat motionless during weeks of excruciating testimony about the rape and murder of his Danvers High School math teacher, was convicted Tuesday of killing her in an assault that horrified many for its sheer savagery and the attacker’s young age.
Chism, 14 at the time of the attack, stood impassively and stared straight ahead as the foreman announced that jurors had found him guilty of first-degree murder with deliberate premeditation and extreme atrocity and cruelty for the Oct. 22, 2013, slaying of teacher Colleen Ritzer in a Danvers High bathroom. Ritzer’s mother, Peggie, cried as the verdict was read, and her husband, Tom, put his arm around her.
Jurors also convicted Chism, who is now 16, of raping Ritzer in the bathroom but acquitted him on an allegation that he raped her a second time in woods near the school with a tree branch. Their deliberations took a day and a half.
The acquittal on the second count of aggravated rape prompted Chism’s mother, Diana, to double over in her seat. Defense lawyers had argued that he should be acquitted of raping Ritzer in the woods, saying she had already died by the time the second sexual assault occurred.
In rendering their unanimous verdict, the Essex Superior Court jury of eight men and four women rejected defense claims that Chism was in the throes of a psychotic breakdown and experiencing hallucinations when he followed Ritzer into the bathroom and attacked her.
A status hearing for Chism’s sentencing is set for Dec. 22.
One of the jurors, Maureen Strileckis, 51, a financial worker from Lynn, told the Globe Tuesday night that it was “obviously very difficult” to put her emotions aside during the trial, but that as a juror she had to do so.
“I found myself directly across from Philip Chism, so it was just a little difficult. . . . I have a son the same age, so it’s something that will give it perspective,” Strileckis said. “But in the end, you’re basing it off the evidence, and you can’t be emotional about it when you’re deliberating.”
During the trial, jurors were presented with horrific evidence, including disturbing security video of Ritzer’s final moments.
“I mean, I guess some of the graphic images and evidence” were hard to experience, she said, “but, again, you had to look at it as evidence whether it was upsetting or not.”
When asked about Chism’s insanity defense, Strileckis said, “It just wasn’t proven.”
Although she is relieved the trial is over, Strileckis said it is something that will stay with her.
“I’ve had a lot of sleepless nights, and I think I will continue to,” she said. “I don’t have any regrets about the outcome, so that’s one good thing.”
Ritzer’s father vowed at a press conference after the verdict to make sure his daughter is remembered for her kindness, while acknowledging that his family faces years of appeals and parole hearings as Chism’s case continues.
“There can never be true justice for the crime that was committed,” he said at the briefing, which was attended by his wife and by Colleen’s siblings, Dan and Laura . “Colleen never gave up, and neither will we. We will not allow Colleen’s death to define how she is remembered.”
Ritzer, 24, grew up in Andover and graduated from Assumption College in Worcester before fulfilling her childhood dream of becoming a teacher.
Richard G. Dudley Jr., a psychiatrist, had testified for the defense that Chism has a psychotic disorder, probably early-onset schizophrenia, that accounted for his actions.
But prosecutors rejected that argument, countering that Chism planned the attack in advance and brought a ski mask, gloves, and box cutter to school on the day Ritzer died.
Essex District Attorney Jonathan W. Blodgett, whose office prosecuted Chism, called the facts of the case “excruciatingly horrifying.”
“This moment belongs to Colleen Ritzer and her family,” he said. “We can’t bring her back, but we can provide some sense of justice for her family.”
The guilty finding on the murder charge prompted defense attorney Denise Regan to have the jurors polled. As Chism sat with his back to Ritzer’s weeping relatives, members of the panel stood up, one by one, and repeated their finding of guilty in front of a rapt courtroom.
Regan declined to comment as she exited the courthouse.
Her work defending Chism is not over. His case in Suffolk County, where he is accused of attacking a state Department of Youth Services worker in June 2014 in an assault that resembled the one on Ritzer, is expected to be heard Wednesday in Suffolk County Juvenile Court.
Defense lawyers acknowledged on the opening day of testimony that Chism killed Ritzer but said he did so while suffering from a serious mental illness. They asked the jury to find him not guilty by reason of insanity.
When Ritzer’s body was found early on Oct. 23, 2013, it was covered in leaves and left near a note that read, “I hate you all.” She had 16 stab wounds to her neck and was nude from the waist down, Essex Assistant District Attorney Kate MacDougall said.
Both sides are now expected to focus on sentencing for Chism, who was tried as an adult for murder and as a youthful offender on the charges of armed robbery and aggravated rape.
Sentencing is likely to be scrutinized given recent court rulings that have put new limits on punishments for juvenile offenders. Superior Court Judge David A. Lowy, who presided over Chism’s trial, is responsible for sentencing him.
Under separate decisions by the US Supreme Court and Massachusetts Supreme Judicial Court, Chism cannot be sentenced to life without the possibility for parole for murder. Blodgett’s office contends that Chism faces a life sentence with the possibility of parole after 15 to 25 years.
For the convictions on armed robbery and aggravated rape, both felonies that carry maximum penalties of life in prison, prosecutors said Chism could be given a life term with a chance for parole after 15 years.
Lowy has the authority to order Chism to serve sentences for each of the crimes concurrently or consecutively, said Carrie Kimball Monahan, Blodgett’s spokeswoman.
Ritzer’s family and her employer, Danvers Public Schools, marked the verdict by encouraging others to carry on her legacy of being good to others.
Peggie Ritzer recalled that her daughter often said, “There is something good in every day.”
“We will carry on and do our best to find the good in every day,” she said.Globe correspondent Lauren Fox and Andy Rosen of the Globe staff contributed to this report. Laura Crimaldi can be reached at email@example.com. Follow her on Twitter @lauracrimaldi.