Graham Dwyer has been sentenced to life in prison for the murder of Elaine O'Hara.
Mr Justice Tony Hunt said it was a sentence "he richly deserves".
Eleven of the jurors who convicted Dwyer of the murder returned to the Central Criminal Court for the sentencing.
Mr Justice Hunt told the jury members he was surprised and delighted to see so many of them in court.
Members of the public queued outside court number 13 from this morning and dozens of people packed into the back of the courtroom.
Ms O'Hara's family were in court, along with women who worked with Ms O'Hara in a newsagents in Blackrock in Co Dublin.
Sergeant Peter Woods summarised the evidence for the court.
After that, the court heard a victim impact statement on behalf of Ms O'Hara's family.
Dwyer, 42, has been in custody since his arrest in October 2013, as gardaí believed he could kill again.
The jury found that he stabbed Ms O'Hara to death on Kilakee Mountain in Rathfarnham on 22 August 2012.
Delivering the sentence, Mr Justice Hunt said we may be thankful this dangerous man is now out of the way.
He said he was satisfied that is what he is. Anyone who thought otherwise need only look at the Buck Special Hunting Knife he ordered from an internet site.
It may not have been used as described by the prosecution but was being kept in a secret place in his office for potential use in the future.
He said Dwyer had been refused bail by the High and the Supreme Court because he was a clear and present danger to others and that was evidenced by the knife and his behaviour in this case.
The judge said he did not know what was up with Dwyer. He had not submitted any reports. He said Dwyer was in a place of denial and delusion.
He said he did not know how long Dwyer would spend in jail.
But he said he had expressed no remorse of any kind.
And there had been the bizarre spectacle of a convicted murderer issuing a press statement which did not refer to the deceased woman.
He said this was a chilling and premeditated murder - almost an execution - after a protracted campaign of the most vile manipulation of a woman too weak to resist.
The judge said it had been a very harrowing trial for the families involved.
He said there were two families involved - whatever one may think of Dwyer.
He said it was very hard to harbour any kind of good thoughts about "this individual" but he said he had a family who were blameless.
The judge said each member of the O'Hara family had been spectacularly courageous and brave in giving their evidence.
He said he could not imagine how profound their ordeal must have been.
He said it was bad enough that Ms O'Hara had disappeared but they had then been subject to this nightmarish scenario of having to sit through Elaine's most intimate details being poked over at the behest of Dwyer.
He said they had given evidence in a dignified composed and measured way and had in no way tried to minimise or gild the lily when it came to Elaine's difficulties.
He said he wanted to say that in the light of the attack on their truthfulness and credibility by a person whose own truthfulness and credibility was on the floor if not below it.
The judge said a trial process was not designed in itself to provide answers to all of the questions raised by people who lost loved ones.
But he said he hoped there were some dark corners of this very dark story into which some light had been shone.
He said the only person who knew the answers to the family's questions had done nothing except tell manifest untruths to date.
He said he had no doubt of any kind about Dwyer's complicity in Ms O’Hara’s demise.
He said Ms O'Hara was cynically misused and abused by Dwyer as part of a prolonged campaign and he said he continued to misuse and abuse her suicidality after her death and right up to the jury verdict.
The judge said another person abused and misled by Dwyer was his wife, Gemma.
He said it was distressing and upsetting to see the pitiful condition in which she had been left by her husband.
The position in which she had been left with two young children beggared belief.
Dwyer shook his head as the judge pointed out that Dwyer bought an 083 phone and reinitiated contact with Ms O'Hara shortly before the birth of their second child.
He said the statement she issued after the trial showed her broad and generous spirit.
He said the scenario of suicide was an agenda set entirely by Dwyer in his jailhouse correspondence.
He persisted in the ludicrous delusion and denial that he had nothing to do with the phones and texts at the centre of this case.
He said Dwyer had no regard for Ms O'Hara as a human being except for what he could get from her - the satisfaction of the perverse and debauched desires to which he was subject.
The judge said shame and embarrassment were in very short supply in Dwyer's corner of the courtroom.
