The critically injured man drove himself to hospital after his smartphone became so covered in his blood, the touchscreen wouldn't register his attempts to dial 000.

On Wednesday Wollongong Local Court heard the emergency was the result of a sudden and unprovoked act of attempted murder by the man's son, 32-year-old Alex Hatzimanolis.

Hatzimanolis was visiting his grandmother and father at their Wollongong home the night of December 24 last year, having spent the evening together visiting other nearby families members.

His dad noticed Hatzimanolis shuffling through a bag as they parked the car outside the home, but when he asked what his son was doing, he replied "nothing".

His father went inside to search for a set of keys Hatzimanolis had lost.

While he was gone, Hatzimanolis pulled a kitchen knife with a 9cm blade from his bag, then followed his father inside.

Once inside, he turned the knife on his father just after the older man handed him his lost keys, grabbing him from behind into a headlock before stabbing him in the throat.

The man fell onto the bed and fought off Hatzimanolis as he tried to stab him again. He was screaming "Alex, Alex!". Hatzimanolis yelled an insult before leaving the property and walking to his own home.

According to a police account tendered to the court, the injured man immediately tried to dial 000 - "however his neck was bleeding freely over the phone and the screen would not recognise his finger pressure. The victim tried to wipe the phone screen but this made it worse".

The man drove the 500m route to Wollongong Hospital, presenting to the emergency department with a deep, 3cm penetrating wound to his neck, and a hoarse voice.

He underwent emergency surgery and remained at the hospital for five days.

Police arrested Hatzimanolis at his home later that night.

He freely admitted to having taken the knife to his father's house that afternoon as "he thought it was time to take his father's life".

He told police he'd had a shot of gin and half a longneck of beer earlier in the day and had also used LSD, cocaine and heroin that afternoon.

He told police he had been prescribed medication for schizoaffective disorder, but that he had not taken his medications in the two days leading to the incident.

In court on Wednesday Hatzimanolis pleaded guilty to causing grievous bodily harm with intent to murder, and to breaching an AVO that was supposed to prevent him from being near family members within 12 hours of using illicit drugs.

The matter will return to court for sentencing proceedings at a later date.