An Ipswich prostitute who had sex with Steve Wright after the fifth victim was found thinks that her life was saved because they were disturbed by an unexpected noise.
Tracy Russell, 31, said she had known Wright for three years and felt safe with him.
But she said Wright was different on the night in mid-December 2006 when she last saw him.
Miss Russell was with Wright at his home in London Road, Ipswich. She said he was "nasty" and she was scared.
And she said Wright lied when giving evidence at the trial:
* lied about not picking up street prostitutes prior to October 2006;
* lied about having sex with vice girls on a yellow reflective jacket;
* lied about donning gardening gloves to remove condoms.
Miss Russell described how Wright "wasn't himself" when they prepared for sex on the bed he shared with partner Pam.
"He pinned me down. He never used to do that. It did scare me when he did it because it wasn't like him. He was a bit nasty," she said.
"He said to me 'I don't want to rush tonight, I will pay you extra. I will pay you £100'.
"Then he heard a bang and he said 'quick, get out'.
"We didn't have sex and that noise probably saved my life.
"It must've been Pam, thinking about it now. I think it could've been a car door. He couldn't get rid of me quick enough.
"He was trying to help me get dressed. He was really nasty. I had never seen him like that before.
"He made me go out the front door, which I thought was weird."
Miss Russell said Wright normally dressed smartly - but that night he was "all sweaty".
"He was always well groomed. He always looked well presented." she said.
"The last night he picked me up he looked all sweaty. He looked like he had been decorating. He had white on his hands. He looked like he had been messing about with cement. He was in jogging bottoms. The other times he was in trousers and jumper."
She added: "His car was immaculate inside that night. It smelt weird, like it had been cleaned."
Miss Russell said Wright lied when he told jurors that he put his reflective jacket and fleece - both of which were spotted with tell-tale forensic evidence - down before having sex and lied about using the bedroom floor instead of the bed.
"The first time I saw the jacket was when it was in the paper," she said. "Trust me, I would've noticed a yellow jacket. That's weird."
She said Wright also lied when he told the court that he had no idea where red fibres - found by forensic scientists in the back of his Ford Mondeo - came from.
Miss Russell said he put a "red picnic blanket" on the back seat before having sex in the car.
And she laughed after hearing how Wright explained the presence of semen on gardening gloves by saying he donned them to remove condoms because he was squeamish - and added: "It's a horrible thought!"
Miss Russell said Wright was also lying when he told jurors how he had never picked up prostitutes before moving to London Road in October 2006..
She said she first met Wright in 2003 and had sex with him a number of times - and he knew "the girls".
"He was Annette's regular as well," said Miss Russell. "I think he picked up Tania once before but she didn't like him. She said 'I'm never seeing him again'. I don't know why she said that.
"Paula saw him. I think she stole his phone once. He knew the girls.
"He liked Annette. If she wasn't around he'd pick me up. I asked Annette about him and she said she had seen him a few times and he was a nice bloke."
Miss Russell added: "Sometimes I chatted to him. He would talk about his work. He had gallstones. I remember thinking 'I don't want to know this'. He went into full detail.
"He said he did have a girlfriend but was having a few problems. It was just wham-bam-thank-you-mam most of the time. I always used to rush him because I wanted to get drugs."
She said Wright would pick her up in London Road and would be waiting in a car.
They had sex in his car as well as at his home.
Normally he paid her £50.
"When I heard he had been charged I thought 'oh my God, I've been in his house. He could've done anything'," she added.
"He was a trustworthy man. I never thought it would be him. I thought it would be someone from another country, or just a maniac.
"He was a nice man. I know most of the girls said he was all right. I didn't have an inkling."