Brandon Libby leaves court after opening statements of his trial in Cumberland County Superior Court in Portland on Wednesday. Libby is charged with murder in connection with the death of his girlfriend Amanda Brown in 2021. Gregory Rec/Portland Press Herald

The state’s case against a Standish man accused of killing his girlfriend may come down to two dueling theories on the shooting.

Brandon Libby, 37, is on trial this week in Cumberland County Superior Court for the murder of 30-year-old Amanda Brown.

The two were living together with their two young children in Standish until, on June 16, 2021, police found Brown dead from a single gunshot wound to the stomach.

He was indicted on one count of murder in November 2021. He has pleaded not guilty.

“Our position is that the defendant shot and killed Amanda with one gunshot wound to the left side of her stomach … with two kids in the house, after an argument on June 14, 2021, a Monday night,” said Assistant Attorney General Bud Ellis in court.

Libby placed Brown’s body in the bed and slept beside her that night, Ellis said. He later left their home for his ex-fiancée’s place in Waterboro, Ellis said, where for several hours he refused police commands to come outside.

But Libby says the shooting was an accident, and that the gun only went off after he tried pushing it from Brown’s hands. She was the one who aimed the gun at him, his lawyer said.

His decision not to call 911, and to leave for Waterboro, were complex reactions to shock – not flattering, but also not direct evidence of his guilt – his attorney Daniel Wentworth said.

“Brandon does feel guilty and did feel guilty – not because he is guilty of murder, but because he accidentally caused her death,” Wentworth said in court.

Attorney Daniel Wentworth looks to his client Brandon Libby while addressing the jury during opening statements in Cumberland County Superior Court in Portland on Wednesday. Gregory Rec/Portland Press Herald

More than a dozen jurors, some of whom are alternates, are scheduled to hear this week from the couple’s neighbors, their family, detectives and various police officers who responded to the murder.

But at the core of the state’s case is a Maine State Police sergeant, overseeing the state crime lab, who set out to reconstruct the actual shooting.

Assistant Attorney General Bud Ellis said that Sergeant Larry Rose’s testimony will show how the gun was actually fired and the trajectory of the bullet.

Rose has previously testified in court that his findings contradict Libby’s story of how the shooting occurred.

Wentworth said they plan to call on an expert from the University of New Haven’s forensic science department to challenge Rose’s account. He questioned Rose’s qualifications, pointing out he was a “detective,” “not a forensic science expert.”

The defense also criticized state police detectives who led the investigation into Brown’s death. They said investigators failed to consider any evidence that would have corroborated Libby’s account, including a complete DNA swab of the gun that might have showed Brown’s DNA on the trigger.

“They put blinders on to try and prove what they already knew,” Wentworth said. “And once they finished their one-sided investigation, they arrested him and charged him with murder.”

Brandon Libby listens as his attorney addresses the jury on the opening day of his trial in Cumberland County Superior Court in Portland on Wednesday. Libby is charged with murder in connection with the death of his girlfriend Amanda Brown in 2021. Gregory Rec/Portland Press Herald

Libby has spent the last three years in jail, waiting for trial. This summer he rejected a plea offer from state prosecutors, even after a judge ruled against his request to throw out various statements he made to police and evidence from a warrantless search of his home.

Shortly before the jury was sworn in Wednesday morning, prosecutors made one last offer for Libby’s plea, which would have capped his time behind bars at 42 years in state prison.

“The offer is off the table as soon as the jury comes in,” Assistant Attorney General Lisa Marchese said.

Libby said he wasn’t interested. If the jury finds him guilty, he could face anywhere from 25 years to life in prison.

This story was updated on Dec. 5 to correct the victim’s age.