Greg Simms has a message for the person who killed his sister Lynette, a young mother-of-two from Sydney's northern beaches, more than 30 years ago.
"To the perpetrator, and you know who you are," Mr Simms said.
"Clearly you don't have any conscience. You have enabled yourself to carry on your life as a lie. There has been no thought or care as to how many lives you have destroyed.
"Wouldn't you want justice if it was your sister who had been murdered? You can only run and lie for so long.
"You have denied Lynn's daughters their mother. You have denied her family and friends a lifetime of events, milestones and happy times.
"If you had any decency you would come forward and allow us some closure and justice for our sister. This also applies to anyone with any information or involved in Lynn's murder."
As the state government on Thursday doubled the reward to $200,000 for information about the disappearance of nurse Lynette Dawson in 1982, police revealed her husband Chris, a former Newtown Jets football star and part-time model, remains a suspect in the case.
But they say Mr Dawson, who now lives in Queensland and is aged in his 60s, is refusing to speak to them.
Police now are appealing for anyone who attended Cromer High School, where Mr Dawson worked as a teacher, between 1979 and 1982 to come forward in the hope they may be able to shed any light on the disappearance of Mrs Dawson.
"I am particularly interested in speaking with former students of the Cromer High School who schooled there between the years of '79 and '82," Detective Sergeant Damian Loone, the officer in charge of the case, said.
"I am also particularly interested in speaking to past or current teachers of that profession who worked or had interaction with the Dawson family, being Chris and Lynette Dawson.
"There are people out there on the northern beaches who know something more than they've told the police. I seek and I appeal to those people with their consciences to come forward."
Wouldn't you want justice if it was your sister who had been murdered? You can only run and lie for so long.
From the outside, the Dawsons appeared to have the perfect life.
The high school sweethearts, who met when they attended Sydney Girls and Sydney Boys high schools, were married, had two daughters and built their dream house at Bayview on Sydney's northern beaches.
But 32 years ago, the reality of their life together came crashing down when Mrs Dawson simply vanished.
The 33-year-old had made plans to take her two daughters to meet her mother for a summer picnic at the Northbridge Baths at Northbridge. She never showed up on that January day in 1982.
She was still missing several weeks later when her eldest daughter was due to attend her first day of kindergarten. Mrs Dawson had been almost as excited as her daughter about the milestone, and would never have missed it intentionally, her family says.
Mr Dawson did not report that his wife was missing to police until six weeks after she was last seen.
In the one time he was interviewed by police in 1991, he did not offer a reason as to why it took so long to report her missing, Detective Sergeant Loone said.
Mrs Dawson was extremely close to her parents and siblings, but they have not seen or heard from her since 1982. Police say they believe Mrs Dawson was murdered.
Her husband has continually denied playing any part in his wife's disappearance, despite a police investigation and evidence at a coroner's inquest that he was an abusive husband. Mr Dawson has never been charged over the case.
On the day of her disappearance, Mr Dawson claimed he received a phone call from his wife in which she claimed that she needed some time away to sort things out.
But Detective Sergeant Loone said investigators do not believe Mrs Dawson was responsible for her own disappearance.
“At the time of her disappearance, Lynette was the loving mother of two daughters – a two-year-old and a four-year-old,” Detective Sergeant Loone said.
“She was also extremely close to her parents and three siblings.
“We think it's highly unlikely that Lynette staged her own disappearance. She had so much to live for.”
Detective Sergeant Loone said he believed there were people in the community who knew what happened to Mrs Dawson.
“We have received some useful information and support from members of the public on this investigation,” he said.
“Yet we do believe there are people out there who know exactly what has happened to Lynette but are either afraid or unwilling to share that information with police.
“If you know where she is, or what has happened to her, please give us a call.
“We don't need to know who you are; all we need is the information you have to hand. You can contact Crime Stoppers anonymously and your call will be treated in the strictest of confidence.”
A 2003 coroner's inquiry into Mrs Dawson's disappearance led to deputy NSW coroner Carl Milovanovich recommended that a "known person" be charged with Mrs Dawson's murder.
The inquest revealed Mr Dawson, then a teacher at Cromer High School on Sydney's northern beaches, had sexual relationships with his students.
One affair was with Joanne Curtis, then a 16-year-old student who would later became his wife.
But despite the recommendation that charges be laid, the Director of Public Prosecutions rejected the advice, citing insufficient evidence.
Detective Sergeant Loone told the 2003 inquest that he believed Mrs Dawson was murdered and her body disposed of between 9pm on Friday, January 8, and 8am on Saturday, January 9, 1982.
Police have urged anyone with information about the case to contact Crime Stoppers on 1800 333 000 or visit the Crime Stoppers online reporting page.