Investigations into dozens of unsolved homicides and long-term suspicious missing persons cases will receive a boost with $64 million in reward money put on the table by the WA government.
Rewards will be standardised and increased to $1 million for 64 unsolved historical cases dating back more than six decades, bringing fresh hope to grieving families.
Les and John Kessey's sister Lorraine disappeared after a night out in Perth's eastern suburbs in December 1977.
They hope the reward for information about their missing sister will lead to evidence or answers "so we can actually put her to rest".
"It's been 46 years and we think about her all the time," John told AAP.
"Not knowing where she is, that's what hurts me the most," Les added.
The brothers said Ms Kessey, who was 21 at the time, was last seen hitchhiking home after meeting friends for drinks.
"That's what they did in the '70s and that was it, that was last she was ever seen," Les said.
"We don't know if anything will come out of this but we hope it will and that someone has enough courage to come forward."
For 39 of the cases, which date back as far as 1958, it is the first time a reward has been offered and for 21 investigations an increase in reward.
Four unsolved homicides or suspicious missing persons cases already had $1 million rewards, reflecting the previous policy of offering different financial incentives for historical cases.
The new reward structure is for information that leads to an arrest and conviction.
Police Minister Paul Papalia said every one of the 64 cases was as important as the next and standardising the rewards recognised this.
"The WA Police Force have always treated every case as equally as important (but) sadly our reward system has not reflected that approach," he said.
"It is a wrong that we are righting today.
"The financial incentive will hopefully ensure those responsible for these heinous crimes are brought to justice."
Police Commissioner Col Blanch said the reward money would help bring closure to the families that had lost loved ones.
"We know there are people in the community who are able to provide valuable information on these unsolved cases which is why we need you to contact us," Mr Blanch said.