The Bunbury Supreme Court judge and jury have been told alcohol and domestic violence were the main factors leading to Wayne Chappell's death.
Debra Jane Alicia Holmes, 54, pleaded not guilty to murdering her partner, Wayne Chappell, 56, after he was found dead from a gun shot wound on July 15, 2018.
The court heard Ms Holmes told 000 operators she had been assaulted by Mr Chappell at their farm residence on Hebb Road, east of Collie, before she shot him.
The trial is expected to run for three weeks, with 30 witnesses to take the stand.
In his opening statement, prosecutor Brett Tooker described the gun that Ms Holmes used to shoot Mr Chappell in the abdomen.
He said the modified .22 caliber bolt action rifle had a magazine of ammunition attached to the trigger guard, via a lanyard, which gave a second option to discharge the rifle by pulling on the lanyard. The jury was told Ms Holmes and Mr Chappell had been drinking in a shed and watching a football game on the night in question, before Mr Chappell threw Ms Holmes to the ground.
Holmes used the rifle to shoot Mr Chappell before she called 000 and told operators she had "had enough".
Ten hours after the incident, Ms Holmes' blood alcohol level was 0.1, equivalent to two times over the legal limit. The prosecution said Ms Holmes provided different accounts of the incident to the 000 operator, Collie police and the Bunbury detectives.
Ms Holmes initially said she had gone into the house to get the rifle and it was shot in anger at Mr Chappell. But, during the interview with detectives, Ms Holmes said she didn't leave the shed to get the rifle and had shot the gun in fear.
Mr Tooker said the State believed Ms Holmes intended to kill Mr Chappell, or at the least, cause an injury likely to endanger his life.
"The accused story is different to the one of the night and she began to engage in a process of self protection," he said.
"It's the states case that Mr Chappell's assault on Ms Holmes made her angry and that this goes a long way to explaining what she did."
Mr Tooker said Ms Holmes had a high tolerance of alcohol, because she was a regular drinker.
The defence argued their client unintentionally killed her partner and was remorseful. Defence lawyer Thomas Percy painted the picture a normal couple with regular issues, which were exacerbated by alcohol.
Following the assault Ms Holmes reflexively picked up the gun lying in the shed in a moment of fear, without intending to shoot Ms Chappell, but to put distance them and warn him not to come closer, he said.
Mr Percy said Ms Holmes accidentally discharged the rifle after stumbling back when Mr Chappell took a step towards her.
"She didn't believe the gun was loaded or intend the gun to be discharged," he said.
He argued the disparity between Ms Holmes' initial recount of the incident and the police interview was due to shock and intoxication.
As day two proceedings began, Judge Anthony Derrick dismissed one juror for "good reason", leaving 14 jurors.
Ms Holmes and Mr Chappell's daughters, Dayna Louise Lancaster, 33, and Tara Lee Chappell, 30, said their parents' relationship was "normal" and "loving".
Both daughters told the court they had never seen their parents in a physical argument and said they rarely fought verbally. But, Ms Lancaster said when they did, her mother would "go on and on until she had to win".
Ms Lancaster said her mother had stayed at her home "a couple of times" after arguing with her father.
She said both her parents liked to drink socially, but her mother would "binge drink", consuming at least two bottles of wine on occasion. She said her father was a "steady" drinker of Jim Beam and Pepsi Max.
Ms Lancaster said she took Ms Holmes to see a counsellor about her drinking habit in 2017. Mr Chappell was a coal industry union delegate on the picket line "fighting for entitlements", which tired her father, she said.
Ms Lancaster said her mother told her she wanted Mr Chappell to go to the doctor about his stress.
The proceedings poured over the locations Mr Chappell kept his firearms, which included in an underground safe in the "new shed" and a separate safe in the old shed. Both daughters spoke of a .22 rifle dubbed the "night-shift gun", which was kept under their mother's bed for protection when their father worked away.
Both the prosecution and defence agreed this was the weapon that caused Mr Chappell's death. Ms Lancaster said she had seen her mother use the gun on "several" occasions, about 15 years ago, to shoot crows that would steal chicken eggs.
"I used to joke about how she was such a good shot," she said. When Ms Chappell took the stand she said she went on the '123 Diet' with her mother a week or two before her father's death.
The night of
The court heard the first two officers on the scene were Collie Police Senior Constable Rodolfo Avellino and First Class Constable David Kamau Ngari.
Snr Constable Avellino told the court when they arrived at 7.50pm, Ms Holmes was standing in the driveway "cradling" a rifle in her arms and talking on the phone.
He said she would not respond to their request over the car speaker to put down the gun and went inside the house and closed the door. Snr Constable Avellino said St John Ambulance paramedic John Thomas, who was also at the scene, called Ms Holmes on the phone and asked her if he could check on the victim.
Ms Holmes put down the gun and eventually allowed officers inside after they promised to call Collie Officer in Charge Heath Soutar.
Snr Constable Avellino said there was an empty bottle of Hardys wine on the table, and a glass on the sink that was three quarters full. Ms Holmes was arrested under suspicion of grievous bodily harm.
He said Ms Holmes asked "several times" if she could drink her wine.
Senior Constable Avellino said Ms Holmes told officers she had wanted to scare her husband.
Defence lawyer Thomas Percy showed the court a photo of the rifle in the back seat of the police sedan, with a bullet-proof vest placed on top, which he described as being "terribly compromised".
First Class Constable Ngari said a gun would usually be placed in a paper bag, but he did not do it because "evidence comes after safety".
He also showed the jury a photo of Ms Holmes' standing, facing the camera, with both hands covered by "disposable overalls", bound by plastic at her wrists.
Senior Constable Taylor, who arrived at the scene shortly after the two officers, did this to forensically secure her hands while they waited for homicide detectives, according to First Class Constable Ngari and Senior Constable Avellino.
First Class Constable Ngari said Ms Holmes' behaviour was "unusual" on the night and she kept asking, 'do I look fat?' First Class Constable Ngari said she told officers she had been "starving herself" for the past week.
"'He kept calling me fat. I've lived with this for 35 years'," First Class Constable Ngari read from his notes. The trial continues on December 5.