The 62-year-old Co Armagh man, Kevin Patrick Fletcher, had always denied stabbing his only son and child Kevin Anthony Fletcher, 32, after giving him a lift home from bingo on 2 September, 2010.
He showed no emotion at the 'Not Guilty' verdict and later, left the Newry courthouse not wishing to say anything to waiting reporters.
It took the Crown Court jury of six men and six women just under an hour and a half to reach their unanimous verdict to acquit Mr Fletcher Snr, who is from Drumarg Park in Armagh.
By their verdict, the jury rejected the circumstantial prosecution case in which it was claimed the once supportive dad had stabbed his son in "an explosive outrage" and that the "tipping point" was his shame at his son "being a child molester" as well as being a drug dealer.
However, trial Judge Kevin Finnegan said that the jury's verdict should not be seen "as an endorsement" in any way of the criticism of the police handling and investigation of the case.
During the trial, the defence had suggested that the police investigation of the murder had been somewhat flawed as they claimed there were any number of people, including an alleged "outraged husband", who could have fitted the bill as a possible suspect.
The defence had contended that the police were "in a rush to judgment" and that they failed to properly investigate a number of matters including damage to the door of the flat, and the fact there were a number of people out looking for Mr Fletcher Jnr and these "other suspects floating about... should have been considered".
Defence QC Patrick Lyttle had also suggested that another motive besides anger, was one of simple robbery of Mr Fletcher Jnr.
He was noted for being "keen on bling", but none of which was found or recovered from his flat after his murder.
During the trial, which started last month, the court heard that Mr Fletcher Jnr, who'd used his mother's phone to call his father for a lift home, had told his landlord Patrick McGee, that a girlfriend had threatened to stab him or cut his throat.
The court also heard that Mr Fletcher Snr picked up his son and drove him to his Castle Street apartment in Armagh where he lived alone.
Mr Fletcher claimed after drinking some coffee with his son, he left him alive and well sitting on the sofa.
However, the following lunch-hour, Mr Fletcher Jnr was found dead on the sofa by his dad, and mum Mary and girlfriend.
There was no sign of forced entry or struggle at his apartment, and no bolts had been locked shut.
Prosecution QC Terence Mooney had claimed this was an indication of his father's guilt as Mr Fletcher Jnr had been fearful for his personal safety and had bolts fitted to the inside of his front door which he kept constantly locked when at home.
The lawyer had also claimed that Mr Fletcher Jnr, who'd once attacked his own mum and threatened to do the same to his dad with a set of dumb bells, was considered a burden to his family and his behaviour had created tension between his close relatives.
The court also heard that he had a history of mental health problems and in addition to being a drug user and dealer who'd been threatened by paramilitaries, he had a conviction for a sexual offence and was under investigation over a series of historical sexual offences at the time of his death.
Although Mr Fletcher did not wish to say anything on Friday about the case, at the time of the murder he had said his son suffered a horrendous death which had left him and his family feeling "just absolutely numb".
He also described his son Kevin as "a lovable lad - although he was a bit of a loner" and that he couldn't "understand why anyone would harm him in this way.
"He was my only child. I loved him with all my heart and soul."
Detectives investigating the murder had said at the time that Mr Fletcher Jnr was the victim of a "brutal... frenzied' attack".