The kidnapping of an intellectually impaired man led to many months of him being physically abused, a jury has heard.

The abuse included him being tethered to a clothes line, forced to sleep in a shed without lighting or heating, having his eyes gouged, his arm stabbed, his foot struck with a spade and a toe hit with a tomahawk.

The attacks on the man and his living conditions were the basis of the Crown's case in the High Court at Rotorua where Leneith Moeke, 36, and Gene Karauria, 29, went on trial on Monday.

Between them they face 24 charges relating to a 32-year-old man described as having the mental age of a young child and lacking the life skills to function as an adult.

Justice Rebecca Edwards suppressed his name in the interim, pending a further order of the court.

Moeke and Karauria have pleaded not guilty to all charges relating to the intellectually impaired man. At the start of the trial Moeke admitted assaulting a child however denied a separate charge of assaulting him with a broom. Justice Edwards convicted him on the assault charge.

The charges the pair face either separately or jointly relating to the impaired man are three of kidnapping, one of ill-treating a vulnerable adult, five of assault with intent to injure, four of wounding with intent to injure, eight of assault with a weapon and three of injuring with intent to injure.

The ill-treatment charge alleges the couple failed to provide him with sufficient food, forced him to shower outside under a hose, doused him in cold war, restricted his use of a toilet, a washing machine, that money was taken from his bank account, he was made to sleep in a shed despite a room being available in the pair's house, that he was prevented from obtaining medical treatment, was verbally abused and made to stand on his head as punishment, as well as sit and stand in one place for extended time periods and that he was made to do unreasonable and excessive household chores.

A number of the charges are representative, meaning they happened more than once. They cover a period from October 2015 to February 2016.

The charge Moeke admitted was dated March 2014 to September 2015, the assault he denied involving the same child allegedly occurred on August 11, 2014 and it's claimed he used a broom as a weapon.

All the offending is alleged to have taken place in the Eastern Bay of Plenty.

Opening the Crown's case prosecutor Hayley Sheridan said the impaired man's family initially wasn't worried about him as he tended to wander so they didn't report him missing. When they did and he was traced to the defendants' home police considered he was okay. She said the man habitually wore layers of clothes to cover his injuries and a hoodie to obscure his face and a "cauliflower" ear.

Ms Sheridan said when the man's clothing was rolled back his wrists were badly scarred from the restraints he'd been bound with.

The man had run away on occasions from the defendants but had invariably returned.

On Christmas Eve 2015 Moeke and Karauira assaulted him because his sister had come to see him, Ms Sheridan said.

When the man asked to go to hospital so his injuries could be treated his pleas were rejected, instead he was forced to wash his wounds in a bucket of salt water.

In his opening statement Moeke's lawyer Gene Tomlinson told the jury there had been no kidnapping, that the man was free to come and go, although he boarded with Moeke he didn't have actual care of him.

Karauria's lawyer Roger Gowing said she was innocent and the allegations against her had been fabricated.

Evidence will begin on Tuesday with the intellectually impaired man the first witness to be called.

The trial is expected to last three weeks.