Thomas Coffin, 37, was jailed for seven years and nine months when he appeared in the Hamilton District Court on Friday.

He beat his terrified girlfriend to a pulp, threatened to kill her and her family, and at one point fired a sawn-off rifle at her.

But Thomas Coffin knew the victim of his frequent jealous rages would be likely to run to the police in order to escape him. That's why, every night, he tied a piece of cord around her throat, wrist, or ankle and then tied it to his own wrist before they went to sleep, to stop her from fleeing.

Thomas John Coffin, 37, was jailed for seven years and nine months when he appeared in the Hamilton District Court on Friday.

He had pleaded guilty to a raft of charges, including injuring with intent to cause grievous bodily harm, commission of a crime with a firearm, kidnapping, assault with a weapon, presenting a firearm at another person, male assaults female and injuring with intent to injure.

They arose from the brutal two-week reign of terror he subjected his 20-year-old victim to in Te Kuiti and Tāneatua last year.

Coffin - a patched Mongrel Mob member affiliated to the King Country chapter - and his victim had been in a relationship for about three years and had a two-year-old son together when they visited the home of one of Coffin's associates in Mokau Rd, south of Te Kuiti, on March 19.

Coffin was jealous of his victim's previous relationship. He became angry, called her a slut, and at one point snatched her phone off her and began looking though it.

The police summary of facts contains no details as to whether he found something he did not like on the phone or if he became frustrated by not finding whatever he was looking for, but he then became enraged and began punching her in the face.

He dragged her by her hair down the hallway to a bedroom, punching her in the head and kicking her in the stomach as he did so.

Once in the bedroom, he continued to kick, beat and stomp the woman for about 45 minutes. Some of the violence was witnessed by their son.

During the night, as she was sleeping in the lounge with her son, Coffin came in several times and kicked her in the back with his foot. The assaults left her with two black eyes, a swollen, blood-encrusted face and extensive bruising to the upper part of her body.

On the ensuing evenings, Coffin began tying them together with a piece of white cord to prevent her from leaving the bedroom. She was allowed to remove the cord once he had woken up.

Sometimes he would whip her with a belt. In one assault, he recorded his partner on his cellphone, and made her say she was a slut. Then he punched her in the mouth.

Coffin owned a sawn-off .22 rifle, which he would point at the woman several times each day. Sometimes the rifle was loaded. While they were at the Mokau Rd house, Coffin used it to shoot at trees.

On one occasion, when she was sitting in a chair out the front of the house, he lined her up from a metre and a half away and asked her if she "wanted to die today".

Then he fired.

The bullet flew past her shoulder, making her ears ring.

Other assaults were precipitated by searches through her phone or Facebook page. Every time he saw the name of a male acquaintance, he would punch her in the head.

In another incident in Tāneatua, he stabbed her legs and feet with a butter knife and punched her in the stomach and head as she was holding a newborn baby.

Coffin told his partner that if she ran away or went to the police, he would shoot her. If he could not find her, he would kill her family.

She finally escaped early one morning with her son while Coffin was asleep and ran to the Tāneatua Police Station.

Later, police spotted Coffin travelling in her car. He sped off at speeds of 160 to 180kmh. Police broke off the chase due to safety fears.

He was eventually located and arrested some months afterward.