The convicted rapist found guilty of murdering missing WA teenager Hayley Dodd has been sentenced to life with a minimum of 21 years behind bars.

Francis John Wark, 61, was found guilty last week of luring the 17-year-old into his car in WA's Wheatbelt in July 1999 and murdering her in a sexually motivated attack.

Her body has never been found.

Members of Hayley's family — including her mother Margaret Dodd, as well as police who investigated the crime — packed the public gallery for on Tuesday's hearing as Wark's sentence was handed down.

Supreme Court Justice Lindy Jenkins said Wark's crime was aggravated by the way he disposed of Hayley's body so it could not be found, something she said had "prolonged and increased the suffering experienced by Hayley's family and friends".

"By your actions after you murdered Ms Dodd, her family has been denied the opportunity to give her a decent burial," she told Wark.

Justice Jenkins thanked the family for their honesty in the victim impact statements they provided to the court

"As I read them, I could feel the pain and despair which they have each suffered … and how that despair and grief had ruined their lives for 20 years."

The keys to a conviction

Wark, who owned a property near where the teenager was last seen, has always denied having anything to do with Hayley's disappearance, but was charged with her murder in 2015 after a cold case review by police.

At the time, Wark was serving a 12-year jail term in Queensland for physically and sexually assaulting a 31-year-old woman he picked up on a remote road in the north of the state.

That crime was one of the main reasons Wark was found guilty of murdering Hayley, with Justice Jenkins finding he had "a propensity to pick up a lone female hitchhiker and to violently and seriously assault her so that she could not resist his sexual assault".

Another key piece of evidence was an earring found during the cold case review embedded in the fabric of a car seat cover seized in 1999 from the borrowed ute Wark was driving on the day Hayley disappeared.

Composite of the earring sketched by Hayley Dodd's friend, and the one found in a car used by Francis Wark. ( Supplied: WA Supreme Court )

Wark's lawyer Daryl Ryan accepted there were "very few" mitigating factors for his client.

However, he urged Justice Jenkins to take into account that Wark had already spent 10 years in jail for his Queensland crimes, and now faced another lengthy term.

"Given he is already 61, there is a likelihood that he will spend the rest of his life in prison," Mr Ryan said.

Francis John Wark was found guilty last week of murdering Hayley Dodd. ( Supplied: Pool )

State prosecutor Amanda Burrows had submitted he should receive a minimum term at the higher end, describing the crime as at the "upper end of the scale of seriousness" and "every parent's worst nightmare".

Ms Burrows said Hayley — who had been walking alone on a remote road — was an "extremely vulnerable" victim, and her murder was aggravated by Wark's refusal to say where he disposed of her body.

"Until she is found the family cannot have the peace they seek," Ms Burrows said.

Ms Burrows also said Wark's offending in 2007 showed that he posed "a continued danger" to the community, especially to women.

Family in pain 'every day'

Margaret Dodd (l) supported by her husband Ray, said the family was deeply wounded by Hayley's disappearance. ( ABC News: David Weber )

Hayley's mother, Margaret Dodd, said outside court the family "goes to bed with pain, and wakes up with pain every single day."

"When Hayley went missing we received a deep, deep wound," she said. "That wound got wider and wider over the years, maybe now it can start to close up.

"We will never get rid of the scars but at least we can start healing."

Mrs Dodd said while she was happy with the sentence, she needed Wark to tell her where is Hayley's body was.

"I hope that he gets a conscience and he turns around and says: 'I've done enough, I have to accept responsibility for what I've done, I will tell the family what I've done with their daughter so they can have some rest and get on with the rest of their lives.'"

Surrounded by her family, Mrs Dodd urged the community to support proposed laws that would see killers who refused to reveal the location of their victims refused parole — a fate she wished on Wark if he continued to remain silent on the location of her daughter's body.