Jasmine McMonagle, 27, was found strangled and beaten to death at her home in Killygordon in January 2019, reports BBC.
Richard Burke of Killiegordon also pleaded not guilty to manslaughter but to manslaughter.
A prosecutor called her death “senseless and horrific”, reports BBC.
Irish broadcaster RTÉ reported that a unanimous verdict was handed down by a Central Criminal Court jury convening in Monaghan.
In her closing remarks, a prosecuting attorney told the jury that Ms. McMonagle was a devoted mother who was much loved by her friends and family.
She also told the jury that no one was suggesting Burke wasn’t responsible for the death.
A defense attorney said Burke accepted responsibility for Ms McMonagle’s death, but mental illness was at the heart of the case.
What happened to Ms McMonagle was “beyond explanation, excuse and beyond words”, he added, reports BBC.
The trial was heard on Wednesday by two psychiatrists, who both agreed that Burke was suffering from a mental disorder at the time of the murder.
That greatly reduced his responsibility, they said, reports BBC.
The presiding judge, Justice Paul Burns, said there was no evidence that Ms McMonagle was anything other than a “good mother and a good person”, reports BBC.
He told the jury to return a guilty verdict to manslaughter or a not guilty verdict.
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