"I suggest to you this isn't going to be a case of whodunnit, the real issue will be what the accused had in his mind," she said.
Ahsee lived within walking distance of the policeman, and described the older man as his boxing coach whom he would regularly visit to work out with in a converted garage gym.
Mr Phillips was working for the New Zealand police at the time as a temporary constable, sworn in to work as a 'jailer'.
On the night of Mr Phillips' death, Ahsee went round to the policeman's flat and was scheduled for a workout.
Neighbours told police they heard two voices and a series of "banging, thumping" noises coming from the usually quiet house, said Ms Jelas.
"A voice said something along the lines of 'Have you had enough ... or I have had enough."
An alarmed neighbour called the police at 10:14pm after Ahsee was heard "yelling and screaming" on his way home, including yells of "I killed someone."
The teenager returned to his family home "emotional and intoxicated" and smashed two windows, so his mother asked police to keep him overnight to detox.
The next day Ahsee confessed to his mother he had stabbed the policeman, and he went to a police station.
"He admits to stabbing the deceased but he said he can't remember anything about it. He can't say what was in his mind," Ms Jelas said.
Police then went round to the Papakura address and found Mr Phillips face down on "heavily bloodstained" hallway carpet. Blood was also splattered throughout the kitchen, lounge, dining room and bathroom and across various appliances, chattels and clothing.
Ms Jelas described Mr Phillips as a gay man who liked young men and was known to proposition them "so to speak".
Police records show Ahsee denied any sexual or physical contact with the policeman, she said.
Ms Jelas also pointed out a pair of blue shorts with the accused's saliva on the crotch area in evidence photos.
The deceased's laptop and cellphone were taken from his house and the laptop was found in Ahsee's family home, while cellphone records traced Ahsee's family using the stolen cellphone days after the death.
The trial is set down to take three weeks.