The mother of a Perth woman who fatally stabbed her de facto during a fight sparked by loud music says he had attacked everyone in the room and she thought he would kill them all.
Tracey Bridgewater, 41, is on trial in the West Australian Supreme Court, charged with the manslaughter of Nicholas Josephs, 44, at their Hamilton Hill home in September 2018.
Mr Josephs became violent after Bridgewater threatened to call police over heavy metal he refused to turn down, assaulting his much-smaller girlfriend before turning on her parents.
That's accepted by the prosecution, but it argues Bridgewater's actions were not authorised, justified or excused by law, saying she should have sought help instead of escalating an already tense situation.
Diane Bridgewater, 60, who was visiting from England with her husband John to celebrate the accused's 40th birthday and meet Mr Josephs, testified he looked angry when they returned home from a beachfront bar.
When her daughter complained about the music, he jumped up from his seat, pushed her backwards into a corner and grabbed at her as she tearfully tried to get free, while Mr Bridgewater pulled at Mr Josephs' shirt, saying he should leave and cool down.
"I said 'what's going on?' Nick said 'you're a fat slag' and grabbed my hair ... I went straight to the ground," Ms Bridgewater said on Wednesday, adding his eyes were "horrible" and "his face had changed".
She said she was terrified as Mr Josephs then put her husband, who has had heart problems, in a headlock, and then pushed him onto a sofa, repeatedly punched him and tried to strangle him.
"John was still. I thought he was dead.
"I thought he (Mr Josephs) was going to kill us."
During the attack on her husband, she grabbed Mr Josephs "by the goolies ... his private parts" but that didn't stop him so she told her daughter to leave.
The accused replied: "I can't mum - he's biting my finger".
Mr Bridgewater said she then recalled seeing Mr Josephs - who threw his partner across the room and at one stage and shouted "I'm going to kill all of you" many times - with a red dot on his shirt.
"I walk over but my legs are buckling from underneath," Ms Bridgewater said.
"I say 'sit down' ... and he told me to f*** off."
He slid down the wall, she said, and she dropped to the floor too.
The deceased's family wept from the public gallery as she testified, while Bridgewater sobbed as photos of her injured, bleeding father were shown.
He suffered a fractured eye socket and a bite mark, while his wife sustained a possible fractured rib, and both were left bruised.
A doctor who examined Mr Bridgewater said tests showed no vascular irregularities from attempted strangulation.
Ms Bridgewater said she recalled her daughter going to the neighbours for help after the stabbing, and the court previously heard she phoned triple zero.