In creating his false alibi, Dustin La Mont told his girlfriend he was self-harming in the shed at the time Nathan Pukeroa was stabbed to death, the Crown alleges.
Prosecution lawyer Steve Hazard told the jury during La Mont's murder trial at the Auckland High Court, that the 26-year-old scratched his wrists to help explain where he was.
"The Crown says this shows how elaborate Mr La Mont was," Hazard said.
La Mont is charged with the murder of Nathan Pukeroa, 24, and for wounding Devaray-Junior Heremia Cole-Kuruaji, 22, with intent to do grievous bodily harm.
The alleged attacks took place in Renton Rd in Mt Albert on December 2 and in the days following police made several appeals for information and asked neighbours to check their properties for weapons.
Hazard showed the jury photos of the knife wounds and said they would present evidence from a pathologist which showed La Mont thrust the knife into Pukeroa's neck with such force it went in further than the blade of the knife.
However, defence counsel David Hoskin said La Mont acted in self defence to two large men trapping him in a cul de sac, threatened him with "being smashed" and swung punches.
They do not deny La Mont fatally stabbed Pukeroa, but say he did not intend to kill him or have murderous intent.
Hoskin said the circumstances surrounding the attacks were "very much in dispute" and urged the jury to remember every story had two sides, keep an open mind and asked them to reserve their judgment until they had all the facts.
"You can't guess, you can't speculate you can't fill in gaps with what probably happened. Probably is never good enough."
The prosecution opened the trial this morning, saying until that night the three did not know each other and "they came from different worlds".
"So what was it that led these otherwise unknown parties to meet around midnight?"
Hazard showed the jury the knife and referred to it throughout his opening statements.
He said La Mont and his girlfriend had moved into the house on Renton Rd in February 2014, next door to a house frequently used by members or associates of the Mongrel Mob.
Over the next 21 months as his neighbours who "were no angels" held loud parties La Mont's annoyance grew into "a state of anger and frustration" which eventually led him to be sat in the courtroom today, facing a charge of murder and wounding with intent, Hazard told the court.
And in the 10 months leading to Pukeroa's death, La Mont set about getting any evidence he could to use in the removal of his neighbours.
He made complaints to his tenancy manager, the police, took surveillance videos and photos of his neighbours' behaviour, a "vast amount" of vehicle registration checks, and shared his frustrations on social media.
At one point he tweeted: "Rarely have I been more provoked to go on a murderous rampage."
And on the night of December 2, La Mont's anger reached a crescendo, Hazard told the jury.
At 8.08pm he tweeted: "Sounds like the mongrel shitf***s next door are having another party. Yipee."
He posted two more tweets before the Crown alleges La Mont chose to go outside armed with a knife to make surveillances of the house next door.
Two men spotted him and there was a confrontation outside. In an interview with police, La Mont said the men grabbed him and tried to punch him so he pulled out the knife but then doesn't remember anything more.
Hazard said La Mont thrust the knife deep into Pakeroa's neck, severing his carotid artery, causing him to die within minutes.
It is alleged he then stabbed Cole-Kuruaji in the right of his neck, narrowly missing his carotid artery and jugular, and with immediate hospitalisation he survived.
Hazard said La Mont then ran around the block, back to his flat and "took immediate action to cover up what he'd done".
He went into the bathroom, washed his clothes in bleach, shaved his beard, washed the knife, then sprayed down the sink with bleach.
La Mont told his girlfriend he'd been in the back shed to create a false alibi, Hazard said.
"Then he disassembled that knife ... he completely took it apart, took the screws out of it then he disposed of that knife in two different places on his way to work."
He also disposed of the clothes in a tip and Hazard said they will present evidence La Mont appeared normal in the days following the attacks.
But despite his efforts to forensically cleanse himself, he was "painted into a corner by the police investigation", Hazard said.
"Things began to unravel for Mr La Mont very quickly thereafter."
Police got a warrant and searched his flat and found his shoes - the last remaining piece of clothing from the attacks - which had Pukeroa's blood on them.
He could no longer deny his involvement in this incident, Hazard said.
He was arrested up to a week after Pakeroa's death.
Hazard said the Crown had to prove beyond reasonable doubt that a murder had taken place and it hadn't been in self-defence.
The jury would do that by considering the motivation of the attack was in response to an attack or whether it was a "cocktail of anger, frustration and retaliation".
"The Crown is saying this was an extreme form of action. Was that relative to the threat?"
The jury will hear La Mont's defence counsel's opening this afternoon as the trial continues. The trial has been set down for three weeks.