The taking of Jozef Puska's DNA by Tullamore gardaí was a crucial step in the investigation, writes Prime Time's Security Correspondent Barry Cummins.
Jozef Puska was brought in the back door of Tullamore Garda Station on the afternoon of 18 January 2022.
The journey from Dublin’s St James’s Hospital had been a swift one.
The Slovak national, with an address in Mucklagh, Co Offaly, had spent the previous five days in the hospital, being treated for stab injuries to his stomach.
During his time in the emergency department, and then the Bennett Ward, Puska had made significant comments to Tullamore detectives, who had been sent to assess him.
Puska had initially said he had been stabbed in Blanchardstown after travelling from Tullamore on the day Ashling Murphy was attacked, 12 January. Then, later on in his hospital stay, he indicated he had caused violence to a woman.
Detectives Brian Jennings and Fergus Hogan were the first to travel from Tullamore to see him.
Their colleague, Det Sgt Pamela Nugent, joined them with a search warrant the following day, on the evening of 14 January. Jozef Puska was moved from an eight-bed ward to a private room.
Speaking through a translator on a phone loudspeaker, that evening Jozef Puska made incriminating comments.
Detective Sergeant Jennings told the trial that, as the interpreter translated, the detective wrote down in his notebook: "I did it, I murdered, I am the murderer."
Work at Tullamore station in the previous two days had been key.
On the day Ashling was attacked, another man had been arrested early in the evening.
A witness had described seeing a man crouched over - or on top of - a woman in undergrowth along the Grand Canal. The witness described the man as having sallow skin, brown eyes, facial hair, and "kind of bald to the front of his head".
A garda thought he recognised the description, and another officer was sent to visit that man. Within two hours of Ashling’s murder, that man was in garda custody.
He would spend more than 24 hours in Tullamore station before being eliminated as a suspect and released without charge.
By the time that man was released, Jozef Puska had travelled to Dublin and was in St James’s Hospital.
Come lunchtime on 18 January 2022, six days after Ashling Murphy set out on her walk along the Grand Canal, Puska was back in Tullamore.
Detective Sergeant David Scahill had carried out the arrest at 10.31am, the moment Jozef Puska had been discharged as a patient from St James’s. He and his colleagues then accompanied Puska on the 100km journey to Tullamore.
After entering through the back door of the garda station, Puska was brought to a processing room. His height was taken and his personal details.
In another room a short distance down the corridor, fingerprints, blood and DNA samples are obtained. He would spend that night in a cell in Tullamore.
His fingerprints in time would be matched to the prints on a bike found abandoned close to Ashling Murphy’s body.
His DNA would also be matched with DNA on the bike, but much more significantly his DNA gave a 1-in-14,000 match with male DNA found under the fingernails of Ashling Murphy.
Evidence would emerge during the trial that Ashling Murphy fought for her life. A witness described seeing how - as she lay in the undergrowth with Puska on top of her - Ashling was moving every part of her body that she could to summon help.
She somehow got Jozef Puska’s DNA under her fingernails. Prosecuting counsel Anne-Marie Lawlor told the jury that Ashling was like an 'investigator’ in her own murder.
By 19 January 2022, one week after Ashling Murphy had gone for a walk along the Grand Canal - one week after she was last sighted on CCTV at 2.55pm heading out of Tullamore to exercise - her killer was brought to court charged with her murder.
By then, gardaí knew that their case would be three-pronged. They had DNA evidence, they had confession evidence, and they had CCTV evidence, and lots of it.
More than 25,000 hours of CCTV was analysed by a small team of detectives led by Detective David Harney at Tullamore station. A lot of the footage was from the day of the murder.
It showed Jozef Puska beginning his journey from Mucklagh into Tullamore at 12.25pm that afternoon.
Numerous cameras followed his journey up Main Street, and then around the garda station.
He was not picked up for the following half hour. In that period it is believed he was cycling around Tullamore Park. At 1.30pm, he was seen again on CCTV. He headed east up Tullamore’s Church Road, and began following the first of two women he would shadow in the town that day.
Beata Borowska had no idea a man was cycling slowly on the footpath behind her. Jozef Puska followed her for six minutes. When Beata went into the local Tesco shop, Puska turned around and headed for the town centre again.
Further up the road, he began following Ann Marie Kelly, who was taking her dog for a walk.
Ms Kelly sensed that something was happening behind her, and paused on the footpath, turning to see a man cycling very slowly behind her.
She told the court that Puska stared at her as he passed by and then continued on his journey.
The last sighting of Puska on CCTV was at 2.05pm at a car park beside the Grand Canal.
Fitbit showed Ashling Murphy's movements and heartrate
Ashling Murphy left Scoil Naomh Colmcille in Durrow at 2:37pm. Her Fitbit watch monitored her heartrate and movement, and would record how she was engaged in activity consistent with exercise from 2.41pm until 3.21pm.
The trial heard that the Fitbit then showed "erratic" or "violent" movements before Ashling’s heartrate began to decrease. By 3.31pm, the Fitbit had stopped recognising a heartbeat.
Gardaí worked through the night in the first week of the investigation. Things were fast moving, and there was a national public outcry.
Senior officers kept the cause of Ashling’s death very close to their chests. Many fellow gardaí didn’t even know.
We often hear that the cause of death in death investigations are being withheld for operational reasons. In this particular case, that decision was to prove crucial.
It was not public knowledge that Ashling had been stabbed when Jozef Puska told Detective Garda Fergus Hogan at St James’s Hospital "I tell her go, I won’t hurt you. When she pass, I cut her neck. She panic, I panic, and then it happened".
Even the gardaí who first went to visit Jozef Puska in St James’s Hospital did not know that Ashling had been stabbed.
Puska knew because he had committed the murder.
His DNA under Ashling’s fingernails would be another firm plank of the prosecution case.
As he made that confession to Det Hogan, Puska also asked how long he might serve in prison.
"Will I go for ten years?" he asked.
In court, Jozef Puska would plead not guilty, but a jury of nine men and three women would find otherwise. After the jury’s verdict, he faces the prospect of spending the rest of his life in prison.
Barry Cummins and producer Sallyanne Godson will have a special report on the investigation into the murder of Ashling Murphy tonight on Prime Time at 9.35pm on RTÉ One.
