Final pitch for defence in Claremont serial killer trial

The accused Claremont serial killer's defence lawyer is making his final pitch, saying elements of the case that don't fit the prosecution's argument must not be glossed over.

The judge-alone WA Supreme Court trial has been going for more than six months, hearing from more than 200 witnesses, but Bradley Robert Edwards did not take the stand and his counsel Paul Yovich did not call anyone to testify.

The ex-Telstra technician committed crimes against three women before the 1996 and 1997 killings, including abducting a teenager from a dark Claremont park and raping her at a nearby cemetery.

That was less than 12 months before the first murder victim, 18-year-old secretary Sarah Spiers, went missing and was never seen again.

Childcare worker Jane Rimmer, 23, and solicitor Ciara Glennon, 27, were found dumped in bushland.

Prosecutor Carmel Barbagallo says the only rational inference is Edwards killed all three women, given they were taken from the outskirts of the same area while walking alone over a 14-month period.

Evidence had "unmasked the killer sought by so many for so long", Ms Barbagallo said in her closing submissions on Thursday.

Mr Yovich then zeroed in on the physical evidence, particularly a trace DNA sample scraped from Ms Glennon's fingernails, which he doesn't dispute came from his 51-year-old client, just how it got there, suggesting contamination in the laboratory or at the crime scene.

He also queried the unknown provenance of hairs found on Ms Glennon, which didn't belong to her or the accused.