Oliver Kierans (57) of Drumbannon Bailieborough in Cavan had pleaded not guilty to murdering Patricia Kierans (54) on September 5th, 2013 at the same address.
A majority verdict of not guilty of murder but guilty of manslaughter was reached after more than fifteen hours of deliberations.
He was found guilty of the possession of a 12 gauge double barrel shotgun and guilty of possession with intent to endanger life last February.
Patricia Kierans died from a shotgun injury to the chest after being shot at quite close range.
The two and a half week trial heard that Patricia Kierans, who had been married to Oliver Kierans for more than 33 years, had moved out of the family home in June 2013.
The jury were told that this did not sit well with the accused who had recently begun drinking again after abstaining for the summer.
The Central Criminal Court heard that out of the Kierans four children, three have moved to Australia along with six of their ten grandchildren.
In his testimony (Feb 19th), Oliver Kierans described a "fixation" Patricia had that he was having an affair.
The court heard that Patricia Kierans was shot with a shotgun at quite close range sustaining a very serious wound to her chest from which she died.
It is the States case that afterwards, Oliver Kierans went to The Square bar in Bailieborough where a "siege" took place and he was found by gardai with a sawn off shot gun.
Throughout the two and a half week trial, the jury were shown CCTV footage in which a man identified as Oliver Kierans is seen pointing a double barrel shotgun at a man identified as local guard, Tommy Fay.
In separate CCTV footage from the morning of September 5th, a man identified by gardai as Oliver Kierans was seen by the jury, entering Clarkes shop in Bailieborough to purchase two naggins of whiskey.
State Pathologist Professor Marie Cassidy gave evidence that the cause of death was a shotgun injury to the chest.
Professor Cassidy concluded that the cause of death was a shotgun injury to the chest which could have been shot from a distance of 1.2 metres or 4 feet and that the injuries were of such severity that death would have been almost immediate.
Ms Justice Aileen Donnelly said today (Monday) that it is "tragic" that Mr Kierans caused the death of Patricia Kierans.
"It is tragic that the defendant caused the death of Patricia Kierans. She took great care of her children," said Ms Justice Donnelly.
"This tragedy was brought about by the criminal act of the defendant. I agree with the jury that the correct interpretation is manslaughter through gross negligence," she continued.
"Regarding the offences of possession of a sawn off shotgun, he was also convicted of unlawful possession and possession with intent to endanger life," she said.
"Oliver and Pat met as teenagers - at the time of the death of Patricia, they had been married 33 years. In spring, early summer of 2013, unhappy differences arose in the relationship," she said.
"Mrs Kierans moved out of the family home and in with her sister and did not have contact with Mr Kierans over the summer - she began a new relationship," she said.
"Mr Kierans sent a number of text messages asking her to reconsider. At 7.30am (September 5th 2013), he went to a shop and bought two naggins of whiskey."
"Oliver Kierans drove to where Patricia Kierans car was parked. Mrs Kierans got into the car on the driver side and Mr Kierans on the passenger side and drove to family home," she said.
"It appears they both went into the house and upstairs to a bedroom. It is the evidence of Mr Kierans that he picked up his firearm with the intention to taking his own life and the firearm discharged in direction of Patricia Kierans."
Speaking outside court, Solicitor Cahir O'Higgins said the outcome was not a happy one for the Kierans family.
"On behalf of the family, I would like to say that while they are pleased he was acquitted of the murder charge, this isn't a happy outcome," he said.
"It is a tragedy for two families. While they celebrate that aspect, they are grieving. There are two tragedies."
Ms Justice Aileen Donnelly sentenced Kierans to nine years for manslaughter, eight years for unlawful possession of a firearm and 12 years for possession with intent to endanger life to run concurrently.