During a sustained attack lasting nearly an hour, he inflicted 21 knife wounds on Ms Hines.
He also stabbed to death their five-month-old baby Amy, her three-year-old son Reece, and her 20-year-old friend Alicia Brough.
Geary was yesterday given four concurrent life sentences. The court heard his murder spree was borne out of jealousy and a determination that Ms Hines, aged 25, would never leave him for another man. It was planned and executed with cold precision.
Geary, aged 37, originally from Milford in North Cork, became enraged when he discovered that Ms Hines had planned to enter a relationship with Englishman Chris Bradley, her childhood sweetheart.
Geary was staying in a rented house at Meadow Court, Newcastle West, with three other men.
After leaving at about 10.30am on the day of the murders, Geary stopped at a deli shop and bought a soft drink. He got to Ms Hines’ house at around 11.30am.
Ms Hines, Ms Brough, and the two children were in the house. Ms Brough left to buy some groceries, taking Reece with her.
When they left, Geary went to the kitchen and took out a knife from the sink. Without warning, he walked up behind Ms Hines and stabbed her in the back.
He grabbed Amy from her arms, and while holding the baby in one hand, he continued to repeatedly stab Ms Hines. He told gardaí that Ms Hines cried out; “Ah no, John. I love you.”
Badly wounded, she crawled along the floor into the living room where she died. He then stabbed Amy a number of times, once in the heart.
A short time later, Ms Brough returned from the shop and on seeing Geary holding a bloodied knife, tried to take it from him. He then repeatedly stabbed her.
He told gardaí that Reece tried to get between him and Ms Brough. Geary turned on the little boy, stabbing him to death.
He told gardaí: “One minute, Reece was roaring for his mammy, then he was dead.”
The attacks occurred between 11.30am and 12.30pm.
Autopsies found Geary had stabbed Amy nine times, Reece 15, Ms Hines seven and Ms Brough 16 times.
He then took the bodies of the two children upstairs where he covered them with a blanket.
He also placed blankets over the bodies of Ms Hines and Ms Brough where they lay.
During the attack he sustained a serious stab injury to his hand and was covered in blood.
Geary found clothes in the house and changed, before walking to his house. The three other men sharing the house saw him return and on noticing he had a serious cut, asked what had happened. He told them he had cut his hand with a glass when playing with a dog. Geary declined an offer to bring him to a doctor. However, he realised he’d left his key in Hazelgrove and so returned, and got it.
He was also armed with another knife he had taken from a drawer in his own house. Gardaí do not know why he brought this knife. However, before leaving the scene, he placed one of the knives used in the attack in Ms Hines’s hand.
Before he left, he locked up the house, meaning gardaí had to force the door when the alarm was raised the following day.
On Leaving the scene, Geary walked to a bus stop near the Courtenay Lodge Hotel and caught the 2.15pm bus to Colbert Station in Limerick City.
In Limerick, Geary bought a pair of gloves and a bandage to cover his wounded hand.
From there, he got a bus to Ennis, Co Clare, before boarding another bus bound for Kilkee.
He got to Kilkee at around 7pm and booked into the Stella Maris Hotel. He had what seemed like quiet social drinks in the hotel bar, before going to bed.
Geary ate a full breakfast the following morning and headed off for a walk along the local cliffs.
Later that morning, he phoned a friend, Gerard Bradley (no relation of Chris Bradley) and told him he had killed Ms Hines and her two children. He then went drinking in a number of bars.
Acting on a report from Mr Bradley, a number of gardaí led by Sergeant John Flanagan went to the house at Hazelgrove at around 12.30pm — 24 hours after Geary had left.
Sgt Flanagan was the first person to enter the crime scene which shocked the nation.
During forensic examination, gardaí found six possible murder weapons. Laboratory examination of the items found four knives and a screwdriver had been used by Geary in his bloody rampage.
At around 4pm, Det Garda Michael McDonagh arrested Geary, who was having a drink at the Central Bar in Kilkee.
After being taken to Henry St Garda Station in Limerick, Geary was brought to the Mid-Western Regional Hospital and subsequently to Cork University Hospital where he had surgery on his hand.
Geary tried to convince gardaí he suffered from depression and mental illness. However, psychiatrists at the Central Mental Hospital formed the view he was fully sane and had no mental illness. Geary did not have a drink or drugs problem, although he had dabbled in cannabis years earlier.
Some nights prior to the murders, Geary went drinking in a number of pubs in Newcastle West where he kept telling people, some total strangers, how his relationship with his partner and mother of his baby had broken down irrevocably.
One Garda source said: “This was building, building, building up inside him after he found out Sarah intended to start a new relationship with Chris Bradley, who was planning to move to Ireland to be with her.
“He was overcome with jealousy and wanted to keep control of Sarah and not allow any other man have her.”