BANGOR – Maine Assistant Attorney General Andrew Benson told a Penobscot County jury Tuesday morning that Mark Barnes beat, strangled, stabbed, then suffocated his mother, 59-year-old Barbara Barnes, in an argument over money.

He reportedly broke her nose and fractured her left cheekbone before putting his hands around her throat and squeezing so tightly that he broke bones and cartilage in her neck and caused blood vessels in her eyes to burst.

Then, Benson said, the 29-year-old man grabbed a pair of orange-handled scissors from the kitchen drawer and stabbed his mother repeatedly in the neck and the stomach. Finally, he said, Mark Barnes wadded up a kitchen paper towel and rammed it down her throat.

On the morning of Dec. 21, 1999, police found Barbara Barnes lying dead on her back, her arms outstretched above her head, in the dining area of her Dryden Terrace apartment in Orono. The upper part of her body was covered with a multicolored afghan and a purple blanket. One of her red moccasin slippers appeared to be resting on her forehead.

Mark Barnes’ trial for the Dec. 20, 1999, murder of his mother, a longtime waitress at Pat’s Pizza in Orono, got under way in Penobscot County Superior Court with a detailed description of her brutal murder. Before Tuesday, the only information released about how she had died was “multiple stab wounds.”

The jury of six men, six women and two female alternate jurors listened intently as Benson described how Barnes fled the state later that night in taxicabs after taking $1,000 in $100 bills from his mother’s apartment. Investigators found $750 in Barbara Barnes’ wallet and several thousand dollars in a desk drawer. Mark Barnes last was seen about 5 a.m. Dec. 21 in downtown Boston. He was arrested the following May in a Manhattan subway.

Defense attorney Jeffrey Silverstein of Bangor reminded the jury that Barnes is innocent until the jury begins its deliberations and each member votes guilty or not guilty.

“This is a whodunit,” Silverstein said at an impromptu press conference during the lunch recess. “There is no witness to place him there or even in the area at the time of the crime.”

He also said that he and his client would make a decision later in the week about whether Mark Barnes would take the stand in his own defense. While the attorney has not submitted a potential witness list, court documents hinted that Silverstein might suggest that another resident of the apartment complex could have murdered Barbara Barnes.

Witnesses Tuesday included the Orono police officer who discovered the body when he went to the apartment to check on her welfare, the paramedic who determined that Barbara Barnes was dead, and detectives from the Maine State Police who processed the evidence at the scene.

Craig Handley, a fingerprint expert formerly with the Maine State Police Crime Lab, testified that a bloody print of an index finger, found on the wooden wing of a living room chair, matched Mark Barnes’ left index fingerprint on file with the Orono police. That was the only clear and identifiable print found in the apartment, he said.

Although, Silverstein did not mention Barnes’ mental state in his opening statement, his mental health was touched upon during the testimony of Jennifer Twardosky of Merrimack, N.H. Her mother, the late Theresa Goody, and Barbara Barnes were sisters. The women lived in separate residences at Sunrise Trailer Park in Orono during the early and mid-1990s.

Twardosky tearfully testified that her cousin changed dramatically when he returned from Florida in 1992. She said that she grew concerned over his mental health and described her cousin as “angry,” “paranoid” and difficult to “have a conversation with because he’d change the subject to wild things,” but said she did not observe delusional behavior.

She said that she heard Mark Barnes threaten to kill his mother on at least two occasions in the mid-1990s. Twardosky said that she and her mother broke off all contact with Mark Barnes in 1996 or ’97 but continued to see Barbara Barnes at family gatherings without her youngest child.

After the lunch recess, Justice Andrew Mead announced he had dismissed a juror for health and work issues. She was replaced with an alternate.

Barnes, now 33, sat quietly at the defense table throughout the proceedings Tuesday. His surviving aunts, their husbands and several of his cousins sat behind the prosecutor’s table on the other side of the room.

The trial continues today.