Shirley Finn's daughter pleads for truth

The daughter of murdered brothel madam Shirley Finn says she has written to the surviving suspects in the 40-year-old case begging them not to take their secrets to the grave.

Bridget Shewring was aged 13 when her mother was shot dead in 1975 in a gangland-style killing that went on to become one of the most talked about and most baffling murder mysteries in WA history.

But after so many years, some potential suspects have already died and others are now well into their 80s.

In the letters to the survivors, Ms Shewring has asked them to clear their consciences by putting what they know in writing so that when they die the details can finally be revealed.

"I do not think there is ever going to be a murder conviction in Mum's case, but if those responsible could just let me know what happened it would make us all feel a whole lot better," Ms Shewring said.

"It has affected our whole family … It has torn our family apart."

Ms Shewring has welcomed news that police have again re-opened the investigation, but she is also realistic about the chances of a breakthrough after so many years.

She said that if police failed to solve it soon, the State Coroner must be given a chance to hold an inquest while it is still possible for ageing witnesses to be called to give evidence.

A formal request is already being prepared by the family for the case to be examined.

Mrs Finn was found slumped in her car with four bullet wounds to the head and rumours have swirled for years about the possible involvement of corrupt police, politicians and rival brothel madams.

But after countless reviews and inquiries, no one has ever been charged.

Ms Shewring says that after 40 years of wondering, the need for answers has now become an obsession for her.

"It is the most important thing in my life … It is all I think about 24 hours a day," she said.

"Now is the time to step forward if you have any information at all, no matter how insignificant you think it may be.

"Every little bit goes to forming the big picture."

She has set up a Facebook page dedicated to solving the crime on which tips and clues can be left anonymously.