Michael Cawley (37) was warned by Judge Olann Kelleher at Cork District Court that he was "a violent man" and could not be allowed to "take the law into your own hands."
Judge Kelleher said the courts were entrusted with delivering justice in Ireland - and citizens could not be allowed to take matters into their own hands.
The court heard that Cawley - who was under severe strain in 2021 after his daughter's murder trial had again been postponed because of the Covid-19 pandemic - spotted Karen Harrington on a bus, boarded the bus, threw her to the ground and repeatedly kicked her.
Harrington was on bail awaiting her murder trial at that point.
Cawley of Leeside Apartments, Bachelors Quay, Cork pleaded guilty before Cork District Court to assault causing harm to Karen Harrington (38) early last year.
Harrington was last month convicted by a Central Criminal Court jury of beating to death Santina Cawley (2) on July 5 2019 at a Cork apartment complex.
Santina - who was the youngest child of Michael Cawley - died from a traumatic brain injury and a severe spinal injury after suffering a fractured skull and fractures to her arm, leg and ribs while in the care of Karen Harrington.
The murder trial heard there wasn't a part of the little girl's body that wasn't bruised with a total of 53 injuries noted by the pathologist.
Doctors said the injuries suffered by the child were "unrecoverable."
Harrington was the then-girlfriend of Michael Cawley who was separated from his wife, Bridget, with whom he had five children.
The 38-year-old had been dating him since December 2018.
She was handed a life sentence on May 16 after being convicted of Santina's murder by unanimous decision of the eleven member jury following a harrowing four week trial.
Michael Cawley appeared before Judge Kelleher at Cork District Court on a charge of assault causing harm to Karen Harrington last year.
The charge was brought contrary to the Non-Fatal Offences Against the Person Act.
He was charged with assault causing harm to Karen Harrington at Merchant's Quay in Cork city centre on January 26 2021, some 18 months after his daughter's death.
Defence solicitor, Frank Buttimer, said his client was pleading guilty to the charge.
Sergeant Pat Lyons said Karen Harrington had boarded a bus to go home at 7pm in Cork city centre when, by chance, Michael Cawley was walking by and spotted her on the bus.
The subsequent assault was captured by the CCTV system on the bus.
"He threw her to the ground and kicked her on a number of occasions," Sgt Lyons said.
The attacked lasted for 10-15 seconds.
Cawley then left the bus and rang gardaí a short time later to inform them what had happened and make himself available for interview.
Karen Harrington received medical treatment and was assessed to have soft tissue injuries to her chest as a result of the repeated kicks she suffered.
The injured party - who was not in court - prepared a statement but Mr Buttimer said it had strayed beyond what a victim impact statement was supposed to be.
Judge Kelleher agreed.
Having read the document in chambers the judge said he was not adversely affected by the non-relevant parts and would only consider what was appropriate to the matter before the court.
Mr Buttimer said his client was under tremendous strain at the time in January 2021 because of his daughter's murder, the repeatedly delayed court proceedings as well as other issues.
"He should not have done it - there may be some degree of understanding as to why he had some degree of a loss of composure," he said.
Mr Buttimer said the meeting on Merchant's Quay that day was entirely coincidental and resulted in Michael Cawley suffering a sudden loss of control and composure.
"He was enraged when he saw the person he believed, correctly as it transpired, that had killed his daughter."
He said his client was now receiving medical treatment and was also undergoing counselling.
Sgt Lyons said that the defendant had four previous convictions, three in relation to a serious assault in Kilrush, Co Clare for which Michael Cawley received a three year prison sentence in 2004.
Judge Kelleher said the assault matter before him was very serious.
"Mr Cawley is obviously a violent man," he said.
"This was a very unfortunate situations. You cannot take the law into your own hands."
"He is a man who engages in violence and has in the past."
But Judge Kelleher said that, given all the circumstances involved, he would impose a suspended 10 month prison sentence.
"He will not get a second chance," the judge noted.
Mr Cawley had the ten month prison term suspended for two years once he entered a €400 bond to keep the peace.
Karen Harrington of Lakelands Crescent, Mahon, Cork is now entering her second month of a life sentence imposed for the brutal murder of the little girl in July 2019 after she had been drinking for several hours.
Her murder trial also heard that she had been smoking cannabis - and had gone back to her apartment in a very distressed state from a friend's home after being insulted and called "a prostitute" by Mr Cawley around 1.30am on July 5 2019.
Michael Cawley had then left Santina alone in the care of Karen Harrington at 3am - and had walked alone into Cork city centre in search of his cousin.
He only returned to Harrington's apartment at 5am.
Harrington had vehemently denied the murder - but was unable to explain how the toddler suffered such horrific injuries while she was alone with her in her apartment.
Extensive CCTV footage showed the only person who had entered and left the flat with Santina at the time involved was Karen Harrington.
In his victim impact statement, Michael Cawley said he arrived back to Harrington's apartment at 5am on July 5 2019 to discover a nightmare scene.
He said he would forever be haunted by the sight of his daughter fighting for her life and having suffered such disfiguring injuries.
Santina was lying naked and blood-spattered on a dirty duvet with clumps of her hair having been torn out.
Her earring stud had also been torn out.
Karen Harrington was asleep on a nearby couch.
She ran from the scene when Michael Cawley demanded to know what had happened to his child.
Harrington ran barefoot from Boreenmanna Road to a friend's house in Blackrock - arriving with her feet bleeding.
The friend later drove her back to the apartment complex when Michael Cawley, in front of gardaí, accused her of being "a monster" and of killing his child.