Dogged detective work uncovered an "intense hatred" of Harris from a love triangle, a voodoo doll, a "contract" killing with a cocktail of drugs, and finally suffocation with a pillow.
Her death was no accident.
In February 2018, nearly two years to the day marking her death, police charged a 30-year-old woman and 26-year-old man with murder.
Yesterday, the pair, Rosana Mairo Morgan and Tyler Baillie, were sentenced in the High Court to spend at least 17 years in prison for the "highly callous" murder.
The Crown case at the trial in August was Harris was murdered on a "contract of sorts" for Vicki Brookes, whose former husband had been in a relationship with Harris - who was her niece.
Brookes "harboured immense and intense hatred" for Harris, according to the undisputed evidence at trial.
"She had assaulted Ms Harris. She had made a voodoo doll of her. She was herself involved in the local drug scene," said Justice Susan Thomas.
"There was evidence she had made threats to kill Ms Harris in the past to the extent Ms Harris was fearful and had developed a safety plan."
While lawyers for Baillie and Morgan disputed the "contract killing" allegation, saying there was no direct evidence, Justice Thomas was satisfied beyond reasonable doubt the pair were involved in a plan to kill Harris in exchange for money or drugs from Brookes.
She has not been charged with any offence, although police say the investigation remains open.
"Without the contract, there would have been no motive for murder," said Justice Thomas.
"At some stage in the days leading up to the murder, [Baillie and Morgan] accepted a contract with Ms Brookes to kill Ms Harris in exchange for approximately $11,000 in methamphetamine and cash."
The original plan was to make it look like Tracey-Anne Harris overdosed on drugs.
To prepare for the deception, Baillie and Morgan experimented by giving GHB to their friends.
On the day of the murder, Morgan gradually administered a cocktail of drugs, including GHB, to Harris in an attempt to induce an overdose.
This was unsuccessful because of Harris' tolerance to drugs.
Once it became apparent the plan was not working, Morgan injected her with a syringe of methadone, potentially mixed methamphetamine.
This was the "hotshot" - slang for an intentional overdose - which five witnesses said Baillie or Morgan had admitted to poisoning Harris with.
According to Shannon Mosen-Taku, Baillie held down Harris while Morgan injected her with methamphetamine.
Mosen-Taku said Baillie told him this while they were in prison together.
Baillie also called Morgan an "amateur", said Mosen-Taku, because she had not put enough meth in the syringe.
The plan was to administer a second injection but Morgan "freaked out" and ran out of the room.
Despite this, Harris slipped into unconsciousness from the toxicity of the drug cocktail and was in critical condition.
But she was still breathing.
So Baillie - who was Harris' cousin - suffocated her with a pillow.
Text messages sent by Morgan on the day of Harris' death were also part of the circumstantial case against them.
"Be home soon gonna finish it off", "Tell Ty it's just about finished ... I love home kill", then at 6.11pm: "I FELL [sic] SICK".
Finally, at 7.01pm, Morgan texted Baillie to say: "We go to your auntie now."
Witness C, who has name suppression, said Baillie went straight to Vicky Brookes' home after being called by police about the death.
The witness said Baillie told Brookes that her niece was dead, then hugged her, before smoking methamphetamine.
Someone else in the house was Blair McNaughton, who said Baillie asked Vicky Brookes when he was getting the "rest of his money".
Baillie said he was owed $8000 and "half an ounce of crack" for the job he did for his auntie, according to McNaughton's evidence.
A few months later, McNaughton and Baillie were in custody together. According to McNaughton, Baillie told him what happened was over Brookes' husband, who was "sleeping around".
Brookes wanted her gone and asked Baillie if he would do something for her, according to McNaughton's account of his conversation with Baillie.
According to the evidence of Witness F, Morgan told her she had been partying with Harris and "feeding her up on rinse" - or GHB - and Brookes would pay her 11 grams of methamphetamine to do it.
The post-mortem examination found GHB, methadone and methamphetamine in Harris' system.
But, viewed in light of other circumstantial evidence, Justice Thomas ruled the drugs in her system to be from an attempt to induce a fatal overdose rather than Harris' own drug habit.
On the day of the murder, Morgan was sourcing different drugs, including methadone, and lying about the reason.
No syringe containing methadone was found at Harris' home, yet police found a syringe cap was found by Harris' body with Morgan's DNA on it.
While questions could be raised about some of the witnesses, in particular the admissions of Baillie and Morgan, Justice Thomas said when taken as a whole, the evidence proved the murder was planned and carried out in exchange for money or drugs from Vicky Brookes.
This proved to be an important point at the sentencing hearing in the High Court at Nelson yesterday.
The mandatory sentence for murder is life imprisonment, but a judge determines the minimum period of time served before an inmate can becoming eligible for release on parole.
In the most serious of circumstances of the murder, a minimum period of at least 17 years must be imposed.
Two of those circumstances were relevant in the murder of Harris, said Justice Thomas.
"One of the key features of this murder is that it was carried out in exchange for drugs and money ... There is no suggestion you were motivated by any kind of personal grievance, nor was this a spur of the moment act. Your decision to kill Ms Harris can only be described as calculated."
This also made the murder "highly callous", another one of the factors which Justice Thomas said made a minimum prison term of 17 years appropriate for both Baillie and Morgan.
The High Court judge said the purpose of a sentencing hearing was not to reflect the value of Tracey-Anne Harris' life.
"It cannot do that. Any sentence imposed will never be able to reflect the devastating effect this has had on them."
Her mother, two daughters and brother wrote victim impact statements for the hearing.
Her eldest daughter was "dismayed someone she grew up with could kill her mother" and Baillie's actions were a betrayal of the family.
Harris' mother describes the "immeasurable pain" suffered by the death of her only daughter.
"She regrets being unable to say goodbye and is haunted by images of her daughter left alone after she died."
• Anyone with information about the death of Tracey-Anne Harris can call Detective Sergeant Ian Langridge on 03 545 9679.
