GRAHAM Dwyer's ex-partner has told the jury in his murder trial that he used to bring a kitchen knife into their bedroom and pretend to stab her during sex.
Emer McShea said he had told her this was his fantasy while they were in a relationship, but he never actually stabbed her.
They had a son together, Sennan McShae (22), and Ms McShea said last November, Mr Dwyer sent Sennan a birthday card with a note saying he was "sure of an acquittal".
She was giving evidence for the prosecution in the trial of Mr Dwyer at the Central Criminal Court.
The jury also heard gardai found files on one of Elaine O'Hara's computers containing information on different ways of killing people, including use of weapons and methods of "picking a target".
Mr Dwyer (42), an architect of Kerrymount Close, Foxrock, is pleading not guilty to the murder of Ms O'Hara (36) at Killakee, Rathfarnham on August 22, 2012.
Ms O'Hara, a childcare assistant from Killiney, was last seen alive near Shanganagh Cemetery in Shankill that day.
Her remains were found by a dog walker in undergrowth in the Dublin mountains on September 13, 2013. The prosecution maintains Mr Dwyer killed her for his own sexual gratification.
Led through her evidence by Sean Guerin SC, for the prosecution, Ms McShea said she was in a relationship with Mr Dwyer in the early 1990s, when they were in college. In 1992, she gave birth to their son, Sennan.
"One night in the course of the relationship, you had a discussion with him about fantasies," Mr Guerin said.
"Yes," Ms McShea agreed.
"He told you that his fantasy involved stabbing a woman while having sex with her," Mr Guerin said.
"Yes, that is right," Ms McShea replied.
"He began to bring a kitchen knife into your shared bedroom and he would pretend to stab you during sex," Mr Guerin said. "I don't think he actually did it."
Ms McShea agreed.
The court heard gardai showed her still photographs from CCTV footage from Ms O'Hara's apartment complex in Belarmine Plaza, Stepaside and she was able to identify Mr Dwyer in them.
The dates in 2012 were January 21, June 23, July 11, July 12, August 13 and August 15.
"I was shown stills initially, and then I was shown video clips," she told the jury.
The court then heard that in November last year Ms McShea came home from work one day and while collecting her post she noticed a card addressed to Sennan. It was in Mr Dwyer's handwriting so she made contact with her son and opened the card at his request.
It was a birthday card and a note inside read: "Everything going well here, all forensics clear and we are sure of an aquittal now that we have a mountain of evidence that it was a suicide."
Sennan McShea then took the stand and agreed with Mr Guerin that in summer, 2006 he spent time in Cork with his grandparents. He was 14 at the time, had been smoking in secret, and his grandmother found out and told his father.
"You had planned telling him yourself," Mr Guerin asked.
"But I hadn't actually got around to it," Mr McShea replied.
His father "hit the roof" and gave him a lecture on the dangers of smoking and got very upset by it.
The court heard that Mr McShea was living in Ballyshannon, Co Donegal, in July 2012 when he was texted by his father who was working on a hospital in Letterkenny.
"I was actually in my home address in Ballyshannon and he collected me and we went to Bundoran together," he said.
He agreed with Mr Guerin that he also identified his father in a booklet of CCTV images at Belarmine Plaza.
Graham Dwyer's younger brother Brendan was also called by the prosecution. He was asked by Mr Guerin if he told gardai in October 2013 about the last occasion he met his brother at Blind Strand in Cork in early September 2013.
"Myself, my dad, Graham, our brother James and James' brother-in-law," were there, he said.
This was the third consecutive trip and before that, Sennan had gone with them, he agreed.
Neither Ms McShea, her son Sennan or Brendan Dwyer, were cross-examined by Mr Dwyer's legal team.
Resuming evidence she had begun on Thursday, Detective Garda Brid Wallace of the Computer Crime Unit told Mr Guerin she examined an Apple Macbook laptop belonging to Ms O'Hara.
Among the files found was a book called 21 Techniques for Silent Killing by Master Hei Long. It had four chapters titled Manual Weapons, Spike, Knife and unchaku.
There was another document in the same folder called Hidden Weapons.pdf, with accounts of various weapons listed. Another document was called Murder Inc the book.pdf by Jack the Rippa. The table of contents included Chapter 1: The Mark, Chapter 2: Unarmed kills, Chapter 3: Edged and Piercing Kills, and Chapter 4: Gun Kills.
This went on to identify "a number of different ways of killing people and identifies methods for picking a target and various ways to kill people", Mr Guerin said.
The jury was shown a series of photographs of dead women hanging that were found by gardai on Ms O'Hara's computer.
The images had been downloaded from a website www.bestgore.com
The court also heard internet searches for Buck Special knives were found, as well as evidence of orders she had placed for sexual "paraphernalia".
On a HP notebook, images saved from Google Maps included some maps of Dublin Mountains, including Cruagh and Killakee Woods.
It also included reservoirs near Roundwood where some of the "items of interest in the investigation" were found.
The trial continues before Mr Justice Tony Hunt and a jury of seven men and five women.