Mauha Huataki Fawcett, known within gang circles as 'Muck Dog', denied murdering Miss Manning, 27, on December 18, 2008.
But the Crown said the 26-year-old either took part in her brutal slaying at a gang pad that night or was party to it.
In March, a jury of six men and six women took just under six hours to unanimously find Fawcett guilty of murder.
This morning, he will be sentenced at the High Court in Christchurch.
Miss Manning's brother Rob, a city car dealer, isn't sure what to expect today.
"Considering his role in my sister's death, I imagine it will be around the 10-15 year mark," Mr Manning said.
"But sometimes when you think people should get harsh sentences, they get light ones, and vice versa.
"I'll just feel happy that he's not going to be able to roam around and hurt anyone else, or at least be party to hurting anyone else."
Miss Manning, a long-time sex worker, had turned her back on prostitution for several months after the sudden death of her sister Jasmine earlier in 2008.
But on the night of December 18, she was back on the streets, trying to raise money to buy Christmas presents for her family.
She was picked up by gangsters at her usual spot at Christchurch's red light district in what the Crown alleged had been a pre-planned and well-organised hit by the Aotearoa chapter of the Mongrel Mob where Fawcett would earn his gang patch.
She was driven the short distance to the Mob's pad at Galbraith Ave.
They took her inside a shed and turned up loud music before raping her and beating and stabbing her with various weapons.
Once she was dead, they stood around her mutilated body and shouted 'Sieg heil' and barked like dogs, the four-week trial heard.
The Crown contended that mobsters, including Fawcett, dumped her naked body in the Avon River.
Fearing the gang would dob him in to police or else take him out over fears he would talk to police, Fawcett fled the city.
Over a series of police interviews, he incriminated himself in the killing, but later back-tracked.
During the trial, Fawcett, who has a British bulldog tattooed on his face, conducted his own defence, with assistance by an amicus curiae.
He claimed police had "coached" him into making false confessions.
The police investigation into Miss Manning's death remains open.
"It's very clear in evidence of this trial that there were other people involved in this murder and we certainly intend to bring those people to justice," investigation head Detective Inspector Greg Williams said after Fawcett was found guilty.
Mr Manning said he hoped others involved in the killing would be brought to justice and he was supporting the police inquiries.
- By Kurt Bayer of APNZ
