Opening arguments and witness testimony began Monday morning in the murder trial of Noah Gaston, who shot and killed his wife, Alicia Gaston, in their Windham home three years ago.

Noah Gaston admitted that he shot Alicia Gaston in the stairwell of their Windham home early on the morning of Jan. 14, 2016. But Gaston told police he mistakenly thought his wife was an intruder when he pointed and fired his shotgun.

Alicia Gaston, a 34-year-old mother, was killed by that one shot. Noah Gaston, now 36, was arrested within two weeks of her death after police say they found inconsistencies in his story of the shooting. He pleaded not guilty to charges of murder and manslaughter, and he has been held without bail at the Cumberland County Jail ever since.

After repeated delays, a jury was selected Friday and the trial began Monday morning in Cumberland County Superior Court in Portland. Attorneys made opening arguments and state prosecutors began presenting witnesses, including the 911 operator who took Noah Gaston’s call and officers who responded to the scene.

The jury, including four alternates, is made up of eight women and eight men.

Because Gaston immediately admitted to shooting his wife, legal experts said a central issue for jurors will be his state of mind and whether he knew what he was doing that early winter morning.

Police arrested Gaston in part because of his inconsistent statements about how close he was to his wife when he fired the gun, which could contribute to whether he recognized her. The jury is likely to hear evidence about the lighting in the stairwell, as well as forensic evidence about Alicia Gaston’s location on the stairs when she was shot.

But proving that he truly believed his wife was an intruder does not necessarily mean that shooting her was not a crime. Maine law does not allow homeowners to shoot intruders in all circumstances.

The judge in the case is Kennebec County Superior Court Justice Michaela Murphy, an experienced judge first appointed in 2007.

Murphy was the judge who oversaw recent legal battles over ranked-choice voting and the expansion of Maine’s Medicaid program during the LePage administration.

She also has presided over numerous high-profile criminal trials, including murder cases. She was judge in the trial last year of David Marble Jr., who was convicted in July of murdering a man and woman from Augusta on Christmas Day in 2015.

This story will be updated.

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