The jury in the trial heard he had a sexual desire for stabbing women during sex, and had stabbed Ms O’Hara to death.
Following a harrowing nine-week trial, Graham Dwyer, 42, from Kerrymount Close, Foxrock, south Dublin, was convicted by unanimous verdict of stabbing 36-year-old Elaine O’Hara to death in the Dublin mountains in August 2012.
Cork-born married Dwyer, who was filmed stabbing sexual partners and admitted having an affair with his vulnerable victim, faces a mandatory life sentence.
Dwyer was remanded in custody at the Central Criminal Court.
Judge Tony Hunt told the court that he “110% agreed” with the jury's decision based on the evidence - which on three occasions was too gruesome for the public to be allowed to remain in the court.
“The question of suicide simply wasn’t there,” the judge told the court.
However, the jury was satisfied that he lured her up the mountain that evening to stab her in pursuit of sexual gratification before disposing of her belongings to make it look like suicide.
Mr Justice Tony Hunt has adjourned sentencing until April 20, when a victim impact statement will be ready for the court
One piece of evidence involved a document found on Dwyer’s computer which relaid a story of a woman being raped, another was a video of Dwyer knifing Ms O’Hara during sex and a series of others revealed unidentified women being stabbed by him during sex.
Images and links from a phone Dwyer owned included women being stabbed, strangled or killed some of which came from a gore website.
On the face of it the married man was living a normal life in a well-to-do part of south Dublin with his wife and children, working in a successful architects’ practice and enjoying a hobby of flying model planes.
Meanwhile all along he had been developing a deviant sexual affair after meeting his victim online.
Dwyer was charged with murdering childcare worker Ms O’Hara, 36, from Stepaside, Co Dublin on August 22 2012, hours after she had been discharged from hospital for psychiatric treatment.
Her troubled life was played out in court including her depression, borderline personality disorder, attempted suicides and her interest in a bondage and a slave-master relationship.
A search of her apartment recovered a printout from a website based on books in which women are slaves who only exist to please men.
The killer’s father Sean, and his sister Mandy Wroblewski, sat feet away from him as he looked on motionless as the verdict was read out.
His sister sobbed while detectives involved in the difficult investigation also wiped tears from their eyes.
The Courts Service said it would be able to provide jurors with professional help.
“This is not a usual occurrence but we can facilitate such supports, with guidance from the judiciary,” a spokesman said.
“It would be wrong to identify or comment on which or any cases this might happen in – except to say that it is not a commonplace occurrence.”