Edwards, 49, of Kewdale, was charged in late 2016 with the murders of the other known Claremont victims, Jane Rimmer and Ciara Glennon.

Western Australian Police Commissioner Chris Dawson said on Thursday that Edwards had been charged with wilful murder over Ms Spiers' disappearance.

The 18-year-old went missing after a night out with friends in Claremont in January 1996 and her body was never found.

She had rung for a taxi from a phone box near the corner of Stirling Rd and Stirling Highway in Claremont just after 2am on a Saturday morning - but when the taxi arrived several minutes later, she was nowhere to be seen.

"This is a significant development in a long-running and high-profile investigation," Mr Dawson told reporters.

He also said the Spiers family did not want to comment during what was a "very traumatic time" for them.

Detectives were looking for a 1992 white Toyota Camry station wagon with the vehicle identification number (VIN) of 6T172SV2109318479, which they believe could help with the investigation, he said.

Edwards will appear in court on charges involving five women on February 28.

The fear that a serial killer was stalking Claremont streets in the 1990s terrified Perth residents at the time and is believed to be Australia's longest-running and most expensive police investigation.

The two other murder victims - 23-year-old child care worker Ms Rimmer in June 1996 and 27-year-old lawyer Ms Glennon in March 1997 - also disappeared after nights out at the same Claremont hotel as Ms Spiers.

Ms Rimmer's body was discovered in Wellard in August 1996, while Ms Glennon's body was found in bushland in Eglington in April 1997.

Edwards is also charged with abducting and raping a 17-year-old girl in February 1995 in Claremont and indecently assaulting an 18-year-old woman during a break-in at a Huntingdale home in February 1988.

Australian Associated Press