He said Ahsee accepted he was the person who stabbed the policeman, but asked the jury to consider what was going through the teenager's mind at the time.
The defence case would "focus on the circumstances leading up to the wound being inflicted because under our law a person is entitled to use force if they are acting in self defence," he said.
Ahsee went to Mr Phillips' house on July 30 last year and left the house drunk, screaming and yelling down the road he had killed someone.
Police found Mr Phillips, a temporary constable, dead in his blood-stained flat the next day. He had been stabbed four times with a serrated knife.
Ahsee lived within walking distance of the older man and told police he used to regularly visit his boxing trainer.
Crown prosecution lawyer June Jelas said the policeman was a known homosexual with a liking for teenage boys and had made physical advances towards them in the past, including touching.
In her opening statement yesterday Ms Jelas told the jury the case was not a "whodunnit", but the issue was what the accused had in his mind.
The jury of six men and six women began to hear from the first of 74 witnesses this morning.
The trial is set down for three weeks.
