The 'other woman' in the love triangle that was Eamonn Lillis's marriage, masseuse Jean Treacy, urged him to tell the truth about what happened on his house patio as he gave her an explanation for his wife's death. She later went on to become a key witness in the case.
aven-haired Ms Treacy, 32, who has gone to extraordinary lengths to protect her privacy, told the Central Criminal Court that she and Lillis met almost every day during their affair. At the time she thought she had loved him, but now realised it was an infatuation.
Ironically, she met Lillis through his wife, who was also a regular at the beauty clinic where she worked in Howth. The beauty therapist said she had been his masseuse for two years before a relationship developed but said she had told her colleagues in Howth Haven salon that she fancied him.
Unfortunately, revelations about her affair with a married man 20 years her senior who was later accused of murdering his wife were bound to catapult her to notoriety.
In a passionate affair, they had sex in Lillis's car and at his home while his wife was away. They exchanged more then 200 text messages and nearly 90 calls in the fortnight before Celine's death.
She had cut contact after the killing, but Lillis sent her a Tiffany pendant, wrapped in a sheet bearing the words of the Beyonce song Halo.
During the trial, she was given special treatment by gardai who whisked her in and out of court through a secure entrance so waiting press photographers could not take her picture.
A solicitor's letter to the media last week was adamant that she did not want to talk to the press or have her picture taken.
It was all a far cry from her quiet, ordinary, respectable country background.
She is originally from Nenagh, Co Tipperary, and comes from what local people describe as a very decent, solid family who live in the Dromin area of the town.
The youngest of three children, she went to school at St Mary's secondary school in the town and spent the last two years doing her Leaving Cert in St Joseph's College,a co-ed secondary school, in Borrisoleigh. She left secondary school in 1996 and worked for several years as a lifeguard at Nenagh Leisure Centre.
She then spent five years working in the marketing industry and studied beauty therapy at night at the Galligan School of Beauty, before she found work, on August 1, 2006, at Howth Haven, where she would first meet Eamonn Lillis a short time later.
One of her friends from the time said: "She was always very friendly and good fun. I'm not surprised she went into the beauty business as she was always into her appearance. She was very much into her clothes and make-up.
Her mother is Bernadette and her father Brendan is a highly respected author, local historian, photographer and musician.
Her father retired from the post of Revenue Collector in North Tipperary County Council in 2004 after 42 years of service. He was also an instructor in the Civil Defence and retired in 2007 after 45 years. He is also a well-known musician and saxophone player who has played at charity gigs over the years. A playing member of Nenagh Brass Band, he was also chairman of the band.
Mr Treacy is a collector of old photographs and has a keen interest in local history and photography, publishing five books.
Jean Treacy has a sister, Siobhan, who is married with two children and lives in Co Kildare, and a brother, David, who is also married with one child and lives in Belfast
Ms Treacy now lives in Dublin but left the country shortly after giving evidence in court.