Andre Gilling and Ashley Arnopp are accused of murdering 39-year-old Stanley Waipouri at his Palmerston North flat in December last year.
The Crown alleges the two accused used the cover of loud music at Waipouri's Rangitikei Street flat to beat him to death.
"Arnopp said he had a huge amount of adrenalin, these are his words...'and I was just powering for hours'," says Crown prosecutor Ben Vanderkolk.
The court was told that a neighbour came to complain about the noise and when the door of the flat opened he saw a body lying on the floor inside with its clothes pulled down.
Later, the police found Gilling and Arnopp in the flat with Waipouri's body and blood everywhere, from floor to ceiling.
"Arnopp was found in the flat at the time in clothing and footwear covered in blood, as were his hands and particularly noted by the police were blood deposits, smears around his mouth and his lips," says Vanderkolk.
The Crown says Waipouri suffered widespread bruising, fractures and internal bleeding. The skin had been torn from his penis and the tip completely removed.
One of his ears had also been severed.
Arnopp and Gilling have pleaded not guilty - and while defence lawyers conceded that the jury might feel disturbed and angry towards the accused, they were asked not to let their feelings get in the way of a fair trial.
The trial will call 29 witnesses and is expected to last about two weeks.