Mark Lavelle (32) was on the drug crystal meth when he carried out the frenzied and unprovoked attack.
Lavelle, originally from Bollingbrook, Swinford but with an address at Basin Street, Dublin, pleaded guilty at Dublin Circuit Criminal Court to assault causing harm to the Dublin and Na Fianna footballer at around 5am on September 20, 2014 at Dorset Street Upper in Dublin.
He also admitted to the assault causing harm to Thomas Smith at Kennelsfort Road Upper in Palmerstown at around 2am on the Saturday morning and to hijacking Mr Smith's car.
Mr Cooper received nine stab wounds to his forehead, eyelid and neck area and spent one night in hospital.
He had no recollection of the assault and gardaí were called to the scene after a passing taxi driver noticed the footballer stumbling along Dorset Street with his back covered in blood.
Officers later followed a trail of blood from where they met Mr Cooper to a nearby chipper and secured CCTV footage from the restaurant.
Lawyers for Lavelle said he suffered from a mental disorder and required anti-psychotic medication. He had been in contact with the State's psychiatric services since his mid-teens.
His 62 previous convictions include assaults, criminal damage, possession of knives, possession of drugs, burglary, robbery, violent behaviour in a garda station, trespass, public order and altering a prescription.
Today Judge Martin Nolan said Lavelle was a “danger to society” and seemed to be unable to stop himself becoming involved in crime or escape from his psychiatric difficulties.
He said this presented serious difficulties to the criminal justice system which had to use the “blunt tools” available to it such as imprisonment. He said his chief duty was to protect society.
Judge Nolan noted that Mr Cooper was fortunate not to have sustained more serious injuries and had gone on to bring huge enjoyment to the Dublin population in his playing career, if not to other parts of the country.
He imposed two sentences of three and a half years which he ordered to run consecutively. He said this unusual step was by reason of the seriousness of the offences and Lavelle's previous history. He suspended the final two years of the total sentence on strict conditions.
Detective Garda Padraig Jennings told John Fitzgerald BL, prosecuting that at around 2am, Lavelle had attacked the taxi driver and taken his car after the driver had picked him up in the city and driven him to Palmerstown shopping centre.
Lavelle was arrested at an Esso petrol station in Maynooth at around 8am when gardai spotted the stolen car and stopped Lavelle.
Lavelle's hands were covered in blood and he told gardai this was because he had haemorrhoids. He told them he had paid €1,000 for the taxi to a man who told him he had stolen the vehicle.
During the hijacking Lavelle put his hands around the victim's neck and demanded the car and cash from the driver. Armed with a Stanley knife he fought with the driver who struggled to get out of the car and away from Lavelle.
Lavelle then drove off in the taxi into the city. He went begging on Dorset street where he met Mr Cooper.
While being questioned about the taxi-driver assault Lavelle asked gardaí; “How was the Dublin footballer? Who was stabbed? Was it Jonny Cooper? Was it a random attack or did they know he played for Dublin?”
A brief victim impact report before the court stated that Mr Cooper was out of work for two weeks. Although he had facial scars it was his understanding that they would fade in time.
He said he was constantly looking over his shoulder in the aftermath of the attack and was apprehensive going to work. His family were also concerned for him.
The court heard that Mr Cooper had played a club match earlier on the day and gone out with his team afterwards to Copper Face Jacks. He remembered leaving there quite late and becoming separated from his friends.
The next thing he remembered was talking to a passing taxi driver who had come to his aid after he saw Mr Cooper stumbling around in blood-soaked clothes.
Patrick Marrinan SC, defending, said that for most of his life his client has been homeless, begging on the streets, abusing drugs or in custody. He said there was a history of violence in his family and his mother was a heavy drinker.
He said Lavelle became abusing alcohol at the age of ten and moved into more serious drugs in his teens. On the night in question he was taking crystal meth, Mr Marrinan said.
Counsel said that on the night Lavelle wanted to return to Mayo urgently to discuss “some rather bizarre topics” with his mother. He said his client he was “not in his right mind” and desperately needed to be in the Central Mental Hospital.