Tim Clark was speaking outside the Launceston Supreme Court after Renae Lorraine Donald was sentenced for her significant role in concealing Tyson's murder.

Donald was charged with being an accessory after the fact to murder in 2017 and on March 12 she changed her plea to guilty.

Ian Rosewall, Donald's boyfriend, had pleaded not guilty to murdering Tyson, but the killer changed his plea to guilty in March.

Speaking to media on Friday, Tim thanked everyone involved in helping solve the case of his beloved son.

"The last two years have put a huge amount of stress on myself and my family. I thank all those who stood by us during our grief," Tim said.

"I pour my heart out to all of the victims' families who are unable to have closure for their loved ones."

Tyson was described as a "bit of a character like his father".

"He was funny and I loved him," Tim said.

For almost nine months after Tyson was murdered and his body was buried in a shallow grave in the backyard of a Mayfield property, Donald sent messages to the victim's family and friends to make it appear he was still alive.

Donald, purporting to be Tyson, said over Facebook messages they were still in a relationship and she was pregnant with twins.

Tim became suspicious of the messages and reported his son missing in March 2017.

Donald and Rosewall also collected almost $17,000 of Tyson's disability payments from Centrelink after he'd been killed.

During sentencing mitigation on Friday, Donald's lawyer Mark Doyle said a mental health report completed on his client showed she had borderline personality disorder and a fear of abandonment.

Donald had been in a relationship with the 24-year-old victim when they moved into a Mitchell Street house with Rosewall in June 2016.

Shortly after the move Donald and Tyson broke up, with the 18-year-old starting a relationship with 44-year-old Rosewall.

Now 21, Donald sat with her arms crossed as her lawyer detailed the report's findings, including there being a power imbalance in her relationship with Rosewall and that she was a victim of domestic violence.

Mr Doyle said Donald's self-worth was linked to her relationship and she had a dysfunctional upbringing.

On July 16, 2016 - the day of the murder - Tyson and Rosewall were drinking and smoking marijuana.

The pair started to hang makeshift curtains in their Mitchell Street house when Tyson told Rosewall to "get me another cone, you paedo dog".

Rosewall "lost it" because he felt the comment was an insult about the 26-year-age gap between him and Donald.

"Angry as hell", Rosewall picked up a hammer being used to hang the curtains and hit Tyson at least four times to the back of the head.

Tyson convulsed on the floor briefly and then stopped moving.

Rosewall put the victim's body in a shed and buried him within a week of the murder. The victim's highly decomposed body was discovered nine months after he was killed.

Donald, 21, lied to police even after Tyson's body was discovered.

She told them she'd recently seen Tyson at Scottsdale and denied accessing his Facebook account.

In a second interview with the police a day later, Donald admitted to accessing her ex-boyfriend's Facebook account on "one or two occasions".

It was not inferred that Donald assisted with burying Tyson's body, but crown prosecutor John Ransom said she was aware of the murder and entered a "joint and sophisticated strategy" with Rosewall to avoid being caught.

Donald was sentenced to six years' jail, with a non-parole period of three years.

A third person, Robert William Broad, was also charged in relation to the murder.

In November, Broad was found guilty by a jury of failing to report the killing of Tyson and he was sentenced to 12 months' jail, wholly suspended.

Rosewall was sentenced to 22 years' jail, backdated to his arrest on April 11. He will be eligible for parole after 12.5 years.