A 19-year-old has been found guilty of first-degree murder in the death of Moncton, N.B., teenager Baylee Wylie.

The jury delivered its verdict in the case of Devin Morningstar on Friday in Moncton's Court of Queen's Bench after 21 hours of deliberations over three days.

Morningstar was also found guilty of arson with disregard for human life.

The courtroom was filled with emotion as the verdict was read. The Wylie family cried and hugged as the jury foreman read the decision.

Morningstar showed no emotion, standing still in a shirt and tie. As he was removed from the court, his mother, Tina Morningstar, could be heard crying from the bench where she has sat throughout the four-week trial.

When the judge acknowledged how hard it is for jurors to review such gruesome evidence and to make such an important decision, the foreman broke down and sobbed openly, as other members of the jury also cried.

Baylee Wylie, 18, was killed last December. Two others — Tyler Noel, 18, and Marissa Shephard, 20 — are also facing murder and arson charges in relation to his death. (Submitted)

Defence lawyer Bob Rideout said it was obviously a difficult case for the jury.

"They all broke down — you normally don't see that."

Rideout said he considered putting his client on the stand but decided against it.

"It's difficult for a young boy like that," he said. "But he gave certain statements to the police and I think that is what caused him some problems and led to this verdict."

Following the verdict, some of Baylee Wylie's friends and relatives released 18 blue balloons — one for each year of his life. As she released her balloons, Amanda Wylie, his mother, said, "Justice for Baylee."

She declined to be interviewed but did say she is relieved.

Tina Morningstar said the trial was difficult for her to sit through, but she had to be there for her son.

"What happened was horrific and anybody would think that," she said.

'The parts where they played Devin's testimony, and seeing him crying and just seeing how upset he was with the whole thing were the hardest parts for me, as being his mother."

She said she'd hoped her son would be found guilty of manslaughter rather than first-degree murder, which comes with an automatic sentence of life in prison with no chance of parole for 25 years.

Two other suspects were charged with first-degree murder and arson after 18-year-old Wylie's body was found with multiple stab wounds in a Sumac Street triplex which was set on fire in three different places.

Tyler Noel, 19, will stand trial in October 2017, and Marissa Shephard, 20, will be in court in May for a preliminary inquiry.

Justice John Walsh said Morningstar will be formally sentenced Jan. 11, and the judge has requested victim impact statements.

The Crown was represented by prosecutors Stephen Holt and Marc Savoie.

Rideout told reporters his client would likely seek an appeal.