A Massachusetts teenager has been found guilty of premeditated murder in the killing of a classmate in 2016.

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Jurors affirmed their decision in open court Tuesday as Mathew Borges, 18, of Lawrence, stood with a blank expression. Closing arguments wrapped up Monday afternoon in the first-degree murder trial involving the former Lawrence High School student.

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Prosecutors said that in November 2016, Borges – who was 15 at the time – stabbed his 16-year-old friend, Lee Manuel Viloria-Paulino, to death because of jealousy over a girl. Prosecutors said Borges cut off Viloria-Paulino's head and hands and threw the mutilated body into the Lawrence River, where it was found nearly two weeks later.

Boston's WFXT saw more family and friends of the victim inside the courtroom Tuesday than during the rest of the trial. Many were seen sobbing several times.

The jury spent about four hours deliberating Monday and announced a verdict had been reached just after 2 p.m. Tuesday.

During the nearly two-week trial, the defendant did not take the stand, and the defense called no witnesses.

>> On Boston25News.com: Family hears graphic testimony in second day of Lawrence teen's trial

"You can’t rely on their theory and if you can’t rely on the prosecution’s case, you just can’t convict," defense attorney Edward Hayden said in his closing statement.

The defense attorney for Borges told jurors during closing arguments that there is no physical evidence linking his client to the alleged murder, and there are too many unanswered questions in the case.

"There's no scene where the body was dismembered. There’s no murder weapon. There's no tool that was used to dismember the body," Hayden said.

>> On Boston25News.com: Trial to begin for Lawrence teen accused of beheading classmate

"Every piece of evidence in this trial over the past three weeks points to one person. [It] points to him. He’s the person who killed Lee Paulino," prosecutor James Gubitose said.

The emotional Viloria-Paulino family sat in the front row, some sobbing quietly. They remembered their loved one by wearing black T-shirts showing his face on the front. The back of the shirts said: "We want answers! We need answers! We need justice!"

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Even though Borges was 15 at the time of the slaying, he was tried as an adult.