The Herald can reveal for the first time how the shocking incident unfolded.
According to the summary of facts, Horton, who has a long battle with methamphetamine addiction, was seen in the early hours of November 6 last year, in Kaikoura, trying to evade police.
At around 1am, while driving a black Mitsubishi, he pulled sharply into a Kaikoura petrol station forecourt after seeing a stationary marked police patrol car further up State Highway One.
After pretending to refuel, Horton pulled out in front of a van and was followed by the police officer with their lights flashing.
Horton took off at speed – and given he was going "well in excess of 100km/h - the officer deemed it too dangerous to keep pursuing.
At around 12.30pm the next day, another police officer spotted Horton's Mitsubishi at a petrol station in Waipara – 120km south of Kaikoura.
The senior constable - on duty in full police uniform and driving a marked patrol car – ran a check on Horton's car and saw that it was involved in a fleeing driver event in Kaikoura the day before.
As Horton drove off, the officer followed and activated his blue and red lights.
Horton sped off towards Amberley, with the officer estimating he was doing at least 160km/h.
Again, it was too dangerous to pursue, but the officer continued driving to Amberley and soon afterwards, coming onto the township's Wineberry Ave, saw the black car parked on the side of the road.
The officer initially thought the vehicle was empty but as he approached, saw Horton sitting in the driver's seat.
Intending to arrest Horton for dangerous driving, the policeman reached for the keys in the ignition.
There was a scuffle, the officer's Taser drawn but reholstered when Horton tried to grab it.
Horton then "began throwing approximately 20 alternating left and right closed fist punches at the victim, striking him repeatedly in the head and face", says the summary of facts.
"A nearby member of the public saw the victim being assaulted and approached the defendant, restraining him in a headlock. The defendant continued to punch the victim while in the headlock," it says.
Horton then suddenly stopped punching and began to apologise to the officer.
The member of the public thought he'd calmed down and released Horton who quickly threw another 20-odd punches at the officer's head.
Pepper spray had no effect, nor did two attempts with the Taser.
During the assault, the policeman tried to handcuff Horton who pulled his hand free with the handcuff still unlatched and swinging loosely.
"The defendant recognised the opportunity to use the handcuff as a weapon and began repeatedly swinging it at the victim's head," the summary says.
"One blow from the cuff hit the side of victim's neck near the carotid artery, causing a puncture wound."
Horton was again restrained by the same member of the public, which stopped the assault.
As the officer was radioing for help, Horton approached him and said: "I'm sorry, can we call it quits and I'll go".
The officer told him to wait, and he would sort something out.
But as Horton went back to his car, the officer sprayed some of his remaining pepper spray through a gap in the window before Horton drove off at speed.
He was later caught in Christchurch trying to sell a female associate $2600 of methamphetamine.
Horton was charged and would later admit four charges, including aggravated wounding of a police officer, failing to stop, dangerous driving, and supplying methamphetamine.
After the attack, police thanked the brave bystander for coming to the officer's aid.
The policeman suffered concussion and several cuts and bruises over his head and face.
The puncture wound to his neck from the handcuffs required surgical glue to close and took about two months to fully heal.
He now has a 1/2cm long permanent scar on his neck.
Judge Jane Farish said there was a clear link between Horton's drug addiction and his offending.
A cultural report helped the judge understand how Horton's life went so off the rails around eight years ago, falling out with his father and turning to methamphetamine.
In 2015, he was jailed for more than three years for supplying meth and since then had "really struggled to get on top of that addiction", Judge Farish said.
Crown prosecutor Will Taffs said allegations around police conduct were rejected and unsubstantiated.
Horton was jailed for five years, with Judge Farish saying it would give him time to complete drug treatment programmes. He was also given a first-strike warning.
