Ms Stack, aged 27, died at her home in Rosegreen, Cashel, Co Tipperary, on February 2.
Coroner for Tipperary South Paul Morris ruled at her inquest in Clonmel that the evidence was consistent with suicide.
Ms Stack’s father-in-law is trainer and former top jockey Tommy Stack, the one-time rider of Grand National winner Red Rum.
She was originally from Enfield in Co Meath and her late father, David Foster, was well-known in equestrian circles but died in 1998 after a horse fell on him. Her mother is trainer Denise Foster.
Members of her family did not listen to the evidence at yesterday’s inquest but were outside the courtroom in Clonmel during the proceedings.
Depositions were read into the record by Superintendent William Leahy and the coroner.
The family’s solicitor, Una Power, thanked the coroner and the gardaí for their handling of the case. “It has been very hard on both families,” she said.
In his deposition, Robert Lanigan said he was best friends with Ms Stack’s husband.
He was aware that they had been “having some difficulties” in the last few months before her death, said Mr Lanigan.
“Lucy had not been feeling herself for a while,” he said. She had gone up to her parents’ home in Co Meath some time beforehand, before returning.
Mr Stack left for South Africa on business on January 29, Mr Lanigan said in his evidence, and was due to fly back to Ireland on February 3.
On Sunday, February 2, Mr Lanigan was at his house when Mr Stack called him and asked him to call over and check on Ms Stack, as he had texted her during the day and she had not replied.
He drove over to the Stacks’ house and had a look around downstairs, calling Ms Stack’s name a few times as he did so and getting no reply.
There was a light on upstairs and he went up and knocked on her bedroom door.
“When I was getting no reply, I knew this was going to be bad,” Mr Lanigan said.
He opened the bedroom door and saw Ms Stack.
“I knew straightaway she was dead,” he said. It was about 5pm and he called the gardaí.
Garda Mark Rabitte said he arrived at the scene shortly afterwards.
There was nothing of a suspicious nature at the scene and no indication of foul play.
He found notes on a table which were addressed to family members, and outlined details of Ms Stack’s funeral arrangements.
Sergeant Karl O’Leary said a note “gave instructions on what the person who found the body was to do”.
Last rites were administered by Fr Christy O’Dwyer, the parish priest of Cashel, and Ms Stack’s body was taken to Waterford Regional Hospital for an autopsy.
Pathologist Fergus McSweeney said there was no evidence of drugs, while blood and urine alcohol levels were not in the toxic range.
Dr Morris returned a verdict in accordance with the medical evidence, adding that the evidence was “consistent with suicide” and he was “satisfied that a suicide verdict is appropriate, having regard to the manner in which the act was performed. There was clear deliberation in the way in which everything was set up.”