Gay man Stanley Waipouri was beaten to death in a frenzied attack that lasted several hours and during which an ear and the tip of his penis were severed, a jury heard today.

The Palmerston North High Court jury today heard the opening statements by the prosecution and defence, during which it was alleged that Ashley Benjamin Arnopp later said of the attack: "I was just 'powering' for hours."

Arnopp, 20, and co-accused Andre Gilling, 18, have pleaded not guilty to murdering Waipouri in Palmerston North on 23 December last year.

The crown alleges that the pair covered the noise of the attack by playing loud music, but that a neighbour who went to the door to complain about the music saw Waipouri's partially undressed body. When police arrived they found both of the accused still at the premises, and blood liberally splattered "from floor to ceiling." Waipouri had suffered external and internal injuries, police evidence was particularly specific about damage and blood around the deceased's mouth.

The defence acknowledged that the jury "might feel disturbed or angry towards the accused," but advised them not to let such feelings intrude on their consideration of the evidence.

The case is expected to last two weeks during which 29 witnesses will be called.