Sigaragh​ Baea​, 22, must serve at least 17 years for the fit of rage in which he stabbed Prasad Somawansa​ 38 times in her Hoppers Crossing home on the night of February 18 last year.

Baea and Mrs Somawansa's son, Wishhasad​, were at primary school together and rekindled their friendship early last year when they crossed paths in the street.

About a week after that chance meeting, Baea arrived unannounced at the Somawansa home and stayed for dinner, only to return later that night and murder Mrs Somawansa, whose son had been paged by his SES unit and whose husband was in Brisbane on work.

During the attack, Priyantha​ Hewage​ telephoned home and realised his wife of 22 years was in trouble when she answered the call. Mr Hewage heard his wife say "You go out, you go out, you go out" and then three times called out "Dos", the name she called her husband.

Baea lived in Australia with his family as a young child but endured a troubled life when his family returned to Papua New Guinea. Justice James Elliott said Baea found it a shock to see that his former classmate was brought up in a loving, supportive household.

"You found the experience of witnessing two loving parents supporting their son in his life and studies quite confronting," Justice Elliott told Baea in the Supreme Court on Tuesday.

"You were jealous of Wish's life."

Justice Elliott said he could not determine the exact reason Baea murdered Mrs Somawansa with a kitchen knife he always kept on him, but found it a brutal and unprovoked attack.

"It was a vicious, gruesome and cowardly attack. You stabbed this defenceless woman in her own home violently and repeatedly ... you only stopped stabbing her once she fell to floor, which is where you left her."

Outside court, Mr Somawansa, with his father standing next to him, said no sentence could make up for their loss. He had no answers for why his mother was attacked.

"I just find it hard to understand how someone like that would do such a thing and how I could trust someone else if someone I thought was once a friend would do that to my own mother," he said.

"She was a beautiful person, she was loving, she was caring and she always wanted to do good for everyone else. I just wasn't privileged enough to spend more time with her and to care for her and to repay her for  making me who I am today."

The court heard Baea spent most of the following day in church contemplating what he did, before admitting his crime to police and then pleading guilty to murder.

He told police that after Mr Somawansa dropped him off at a shopping centre, he returned to the Somawansa house to look for his myki card. Mrs Somawansa asked him to leave as she was on the phone to a friend.

Justice Elliott said Mrs Somawansa had shown Baea only hospitality and courtesy, and that it was plain by her family's victim impact statements that she would be "greatly missed".

Despite that, the judge said he could not be satisfied Baea had "murderous intent" as he walked to the house, although he was clearly angry.

Baea was effectively abandoned by his parents as a teenager in Port Moresby, when his mother returned to Australia and remarried and his father began a relationship with another woman, which left Baea to raise his younger sister.

Baea was in Australia after visiting his mother when he met Mr Somawansa. He was due to return to Port Moresby three days after the murder.