The man on trial for murdering Emma Caldwell said he had "consensual" sex with her months before her death.
Iain Packer said he did not stop immediately after the 27-year-old sex worker said words to the effect of "stop" or "enough" during the encounter in Glasgow in August 2004.
The 51-year-old denies strangling Ms Caldwell and dumping her body in woods in South Lanarkshire in April 2005.
He denies a total of 36 charges involving multiple women.
The prosecution has withdrawn 10 charges against Mr Packer. He was formally acquitted of those allegations after the Crown closed its case.
Ms Caldwell's body was found in a ditch in Limefield Woods near Biggar five weeks after she was killed.
The murder charge alleges Mr Packer assaulted Ms Caldwell by restraining her, grabbing her wrists and strangling her with his hands and a cable.
Mr Packer was sworn in at the High Court shortly after 10:00 GMT and began taking questions from his defence lawyer Ronnie Renucci KC.
He arrived at court using a walking stick and wearing a zipper jacket, a T-shirt and navy trousers on the 18th day of the trial.
Speaking about the incident in 2004, which took place behind some billboards hidden by bushes on Glasgow's London Road, Mr Packer said he felt "a bit ashamed" and that he should have "stopped straight away".
Mr Packer was also asked about an alleged rape he has been accused of in the early 1990s when he was 16 and the complainer was 14.
He told the court he was "shocked" when he first learned of the allegation.
Mr Renucci asked: "Did you ever rape her or touch her inappropriately?"
Mr Packer replied: "I never."
He also told the court he started using sex workers when he was 18 years old and used them a lot, although he said he did not have an addiction.
Jurors heard he would drive to an area known as "the drag" to pick up sex workers, as well as Glasgow Green, using his work van at different times of the day.
Mr Packer also said he would pay for sex at various saunas in Glasgow.
Jurors previously heard Mr Packer gave a statement to police in which he described an occasion where he continued to have sex with Ms Caldwell despite her asking him to stop.
He also told detectives he had "lied" about not knowing her.
The trial has heard that Mr Packer told police he had driven to an area in Lanarkshire with women, including "six times" with Ms Caldwell.
He was also said to have directed officers to the remote spot in 2007.
On Tuesday, when asked how many times he had been to Limefield Woods with sex workers, Mr Packer replied: "Maximum of six times."
He said he used sex workers more often as he got older and that it was fair to say he had used a "large number" over the years.
The trial before Lord Beckett continues.