The first Crown witness in the first-degree murder trial of Devin Morningstar testified she heard screaming and banging coming from a bedroom next door to her home at 98 Sumac St. in Moncton on Dec. 16, 2015.

Helen Mandy testified she heard what sounded like a man yelling, "You ratted to the police and stole from us."

Mandy said a panicked voice replied, "I wouldn't do that. I love you guys."

Morningstar is accused of killing Baylee Wylie, 18, in December 2015, then setting fire to the Sumac Street triplex where the his body was found.

Mandy testified the noise continued at 10:30 p.m. and it was more aggressive.

She said she heard someone say "Stop yelling or I'll shove this down your throats."

That was followed by sounds of banging metal.

Mandy then called her sister who came over to her apartment with her boyfriend. They would later leave after the noise had calmed down.

Mandy testified she fell asleep at 1 a.m. The next thing she remembers was firefighters breaking down her door at 4 a.m. to remove her and her children from the building.

Baylee Wylie's body was discovered in a residence on Sumac Street in Moncton last December. (Submitted) Morningstar has been in custody since his arrest in December.

Two other people are also charged with the same murder.

Tyler Noel and Marissa Shephard both evaded the RCMP for weeks, wanted on a Canada-wide warrant.

Noel, 19, was arrested near Elgin Jan. 9. He is also accused of arson, and is scheduled to face those charges in the Court of Queen's Bench in Moncton from Oct. 24, 2017 to Jan. 26, 2018.

Shephard, 20, evaded police for 10 weeks before being arrested at a hotel in Moncton only a few kilometres from where the murder happened. She is scheduled to face a preliminary inquiry starting May 1, 2017.

Walsh told the jurors Wednesday they are the judges of the facts while he is the judge of the law. He also stressed discretion was key in serving on a jury.

"What goes on in the jury room stays in the jury room, you take that to the grave with you," said Walsh.

Morningstar's trial is expected to last five weeks.