A Tasmanian man accused of attempting to kill his young sons and wife drove across the state with knives and a cricket bat intent on making her "pay", a jury heard.
Damian Leslie Harper has pleaded not guilty to three counts of attempted murder, one count of wounding, and aggravated burglary.
Deputy Director of Public Prosecutions Linda Mason SC told the court the 47-year-old travelled from his Hobart residence to his in-law's home, where his wife and sons were staying, in January 2019.
In the Burnie Supreme Court on Thursday, the jury heard he broke into the Cuprona home, in the state's north-west, in the early hours of the morning through a partially opened kitchen window and entered the bedroom where his sons were sleeping.
It heard he then cut at his four-year-old son's neck with a Stanley knife, before reaching for his six-year-old son on the upper level of the bunk bed they were sleeping in and telling him to come closer.
Ms Mason said the mother was awoken by screams and tried to get the children away from Mr Harper, but he held her against the wall, stabbing at her and telling her he would kill her.
Mr Harper then allegedly slashed at his father-in-law with the knife as he entered the room to intervene.
But the father-in-law was able to restrain him and place the knife out of reach, before Mr Harper lunged past him, grabbed the knife and cut at his own neck, the court heard.
'Mummy got cut'
Defence lawyer Greg Richardson did not contest that Mr Harper entered the home wielding a weapon, but said the trial must consider his intentions at the time.
"This trial is about mental elements of crimes," he said.
"Virtually all the factual assertions will not be challenged. This trial is all about the mental elements. About what his state of mind was: what his capacities were.
"The primary issue is, what on earth was going on in his mind."
The youngest son, who gave evidence via a pre-recorded video, said he woke to his father in the bedroom.
"Mummy got cut," he said.
Mr Harper's mother-in-law told the court she awoke to the screams of her grandchildren.
"I thought they were having nightmares again so I didn't react straight away," she said.
"The screaming became very piercing and continuous."
Ms Mason told the court Mr Harper had accused his wife of having an affair while she was on a work trip in 2018, and the relationship quickly deteriorated.
She left with their two children to stay with her parents in Cuprona shortly after.
The court heard a week before the incident, Mr Harper, his wife and their children met in Devonport to discuss future custody arrangements.
"The state alleges that these matters are all relevant to what the accused may or may not have been ruminating about, that prior to meeting … in 2019 the accused hadn't had much contact with [his wife] or children, and he was very upset about the meeting and blamed her for the predicament he was in," Ms Mason said.
The alleged attacks occurred a week later, coinciding with their seventh wedding anniversary.
The court heard Mr Harper was frustrated by his situation and "intent on making her pay".
