A love rival of the accused Claremont serial killer has told a court Bradley Robert Edwards threatened to murder him over an affair that included secret sex as the ex-Telstra technician slept in another room.
Edwards, 50, is charged with murdering Sarah Spiers, 18, Jane Rimmer, 23, and Ciara Glennon, 27, in the mid-1990s during his marriage breakdown after his first wife had an affair, resulting in the birth of a child.
The man, whose identity is suppressed, testified in the Western Australia Supreme Court on Monday via video link from overseas, saying the last time he heard from Edwards, the accused threatened to kill him.
"Bradley called and was speaking to (his first wife), who in turn put the phone on to me, and he accused me of having an affair with (her) and I said to him, 'I thought that was plain and clear to see'," the man said.
"He said 'oh, I'll kill you', and I said, 'Well you know where I live, you've got my address'."
Contradicting the first wife's evidence, the man said they had sex before he became their boarder and the affair continued after he moved in.
"She would sneak into my room while Bradley was still asleep," he said.
"I thought she was playing a dangerous game."
The man said when he met the first wife he did not know she was married and accepted her offer to go horse riding with his children.
He then asked her out to dinner and they had sex, then they saw each other whenever they could, although it was some time before they had sex again.
"I believe we were both in a situation where we were craving something," he said.
"I didn't really have anyone that I could connect with.
"I wasn't intending to break anyone's marriage."
The man said the wife came to his home about half a dozen times and on one occasion she had car trouble, requiring Edwards to help jump start the vehicle before the married couple made a "quick exit".
His evidence contradicts the first wife's testimony that the man was a close friend and they started a sexual relationship towards the end of 1995 after he moved into the marital home.
She said at one stage, Edwards saw her hugging and kissing the man on the cheek as they sat on his bed, but he barely reacted and the boarder remained.
The man testified they were actually caught kissing on the lips after looking through photographs together, including one from when she won a Miss Wet T-shirt competition.
"The door opened and I thought oops," he said.
Believing he had "overstepped the boundaries", the man began packing up his things, but the first wife spoke with Edwards then told the man to stay.
"I don't fancy sleeping here another night knowing what he's got in his room," the man told the first wife.
But he was interrupted by prosecutor Carmel Barbagallo and prevented from elaborating.
The man said both he and Edwards cried when they spoke about the incident and Edwards told him to stay.
He later moved out because he felt he could not remain at the matrimonial home, he said.
Under cross-examination, the man agreed Edwards treated him courteously after the kissing incident.
He also agreed Edwards did not know about their sexual relationship while he was living at the house.
The court previously heard Edwards and his first wife separated between late 1995 and early 1996, and she eventually moved in with her lover.
But the man's evidence contradicts some key dates in the prosecution's timeline, which are relied upon to show Edwards' "emotional upset" coincided with the murders.
Defence counsel Paul Yovich repeatedly poked holes in the man's memory, including where he was living on certain important dates.