Mum hopes $1 million reward will solve 40-year murder mystery

Lisa Marie Mott's mother is still seeking closure 40 years later. Photo / WA Police Force

The mother of a Western Australian girl who vanished 40 years ago says she has almost given up hope of ever learning what happened, but is optimistic a A$1 million reward for information may finally solve the murder mystery.

Lisa Marie Mott, 12, was last seen about 8.30pm on Forrest St in the town of Collie on October 30, 1980.

She had just left the basketball courts and was expecting to be picked up by a family friend to go home.

Exactly 40 years later, her grieving mother Marion Flower, 77, has pleaded for closure.

"She was very thoughtful and she had a lovely nature — she always smiled," Flower said about Lisa on Friday.

"If you are still out there, Lisa, somewhere, I still love you, I still love you to bits."

Earlier this month, the WA government announced a A$1 million reward for information that leads to a conviction in Lisa's suspected homicide.

Flower said at the time of Lisa's disappearance, other girls had gone missing in WA.

"I did fear this happening, but at the same time I thought Collie was safe," she said.

"When Lisa first disappeared, I went into shock and ended up in the Collie Hospital in the middle of the night.

"I was screaming and could not stop myself. The night sister put me under a shower and left me there until I calmed down."

Since then, Flower said she had been in a "state of waiting for the other shoe to drop" for most of her life.

"I suppose in a lot of ways I've given up hope that I will ever know, and it's hard not to do that," she said.

"My only hope is after all this time that somebody is still alive that might know something because it's a long time ... a lot of things have changed."

Flower said she still struggled to talk too much about her daughter.

"I can't talk about Lisa very much, as it still hurts too much," she said.

"I have to stay in the present, so all the work I had to do to cope stays in place."

There have been many theories about what happened to Lisa, including that serial killer David Birnie was involved.

He took his own life in prison in 2005.