Tipene died in Auckland Hospital about four hours later.
Defence lawyer Lorraine Smith said her client accepted what he did was wrong.
"When Vincent Skeen was 16 years old he picked up a bottle and he hit another boy with it. That boy tragically died and it changed the lives of two families forever," she said.
"The Crown must prove Vincent had a conscious appreciation of the risk of death and decided to take that risk."
She said there was "huge doubt" over whether that was the case and urged the jury to remember that everything happened very quickly.
"The whole Crown case is based on Vincent Skeen having time and appreciation to know exactly how that bottle had been broken, then to decide to use it knowing Luke's death was a probable consequence," Smith said.
"The Crown saying Vincent was aiming for Luke's throat is a complete overstatement of the evidence. The other very realistic possibility is that Vincent was swinging out blindly without any intent to connect with any particular part of the body."
Smith stressed Skeen had been struck in the head twice before causing the fatal blow and had been drinking that afternoon too, both of which could have clouded his judgment.
She told the jury during her closing address this afternoon that the Crown case simply lacked logic.
"Do you really think if Vincent had turned his mind to murder, he would have continued in front of multiple witnesses?" she asked.
The lawyer also addressed the evidence of Carl Jota who told the court this week that Skeen announced: "I stabbed that c***", immediately afterwards.
"You don't convict a young man of murder simply because you don't like the language he used. Doesn't that admission simply tell you Vincent had not foreseen or intended fatal harm?" Smith said.
"As a matter of common sense you don't announce to the crowd you've just murdered someone."
She pointed to the witness who spoke to Skeen moments later.
Dominic Bellfield said the defendant told him "I caked it".
"He stuffed up. Something happened that he didn't intend and did not foresee," Smith said.
Tipene and his cousins had gone to Grey Lynn that night after they had heard their friend may get into a fight.
But Smith rejected any painting of the victim as a Good Samaritan as "simply rubbish".
Justice Mary Peters will sum up the case on Monday morning before the jury of seven men and five women begin deliberations.
