A Perth newspaper editor who revealed a historic rape case connection in the Claremont serial killer investigation says police missed important evidence early on.

Sarah Spiers, Jane Rimmer and Ciara Glennon disappeared from the upmarket Perth suburb between January 1996 and March 1997.

Ms Rimmer's body was found in August 1996 in bushland at Wellard south of Perth, while Ms Glennon's remains were found in April 1997.

Ms Spiers' body has never been found.

Yesterday, police took a man into custody and are believed to be interviewing him in connection with the killings.

The deaths sparked Western Australia's longest-running and most expensive police investigation.

Newspaper editor Bret Christian has covered the hunt for the killer for decades. ( ABC News: Emma Wynne )

Perth's Post Newspapers reported last year that police believed the person responsible for killing the three women also raped a teenage girl in the year before the first murder.

Editor Bret Christian said police had initially ruled out a connection between the rape and subsequent murders, a decision he believed was flawed.

"I think that led them to ignore what was possibly very important evidence," he said.

"Because here was a survivor who had experienced and interacted with the perpetrator of the three subsequent murders."

'Monstrous story' which captivated and horrified state

Mr Christian, who has followed the Claremont serial killer investigations for much of his career, said the arrest of a man sent a shiver down his spine.

He said the news gave him hope the investigation was finally reaching a conclusion.

"A shiver went down my spine when I heard they picked somebody up, as it did with everybody else I have spoken to, people have had a physical reaction to it," he said.

"It's a monstrous story. It's captivated Western Australia. Especially Perth's western suburbs. It's captivated and horrified us.

"I felt 'I hope they've got him' but you can never be sure.

"This case has a long way to run. It's been 20 years and let's hope it's coming to an end."

Suburban district rocked by crimes

Police remained at the Kewdale home this morning, where forensics officers are continuing a full search of the property.

It is understood police have been in contact with the families of the murdered women to keep them abreast of the latest in the investigation.

The ABC has contacted the family of Ciara Glennon, who declined to comment.

Mr Christian said he hoped the arrest in Kewdale would lead to closure for the families of the women, and for the people of Claremont.

"The thing that horrified people about these murders was that they happened in a quiet suburban shopping centre, that had a couple of entertainment places," he said.

"And they were places where the victims had been with their mums shopping. And they felt safe.

"After dark they would go there and three of them just vanished.

"It was absolutely horrifying, and it became a national story and has been for 20 years."