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 was sentenced at the High Court in Christchurch in front of a packed public gallery.
"It is hard to understand any reason that would justify such a brutal homicide,'' Crown prosecutor Phil Shamy said.
Fawcett had refused to engage with the writing of a pre-sentence report, which Mr Shamy said was "quite remarkable" given what he was involved in.
With the bulldog tattoo on his face, and through his actions, Fawcett was proud to be part of Mongrel Mob, the Crown said.
"There is little Mr Fawcett has done to endear himself to this court.''
Miss Manning, a sex worker, was working on the night of December 18, 2008, when she was picked up 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 where she was raped then beaten and stabbed.
The Crown contended that mobsters, including Fawcett, dumped her naked body in the Avon River.
During his 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.
Today, Fawcett's amicus curiae, lawyer Craig Ruane, said the convicted killer took a "relatively minor role in something that grew beyond his control".
Senior patched members would have been responsible for organised the hit, while prospects like Fawcett, just "do what they are told".
Miss Manning's long-time boyfriend and minder, Kent Gorrie read a victim impact statement to the court.
He paid tribute to a "talented, gifted, bundle of joy" whose love was so treasured.
"You took that from us for that pathetic role you wanted to play,'' he told Fawcett.
It was a "weak and shameful attack", Mr Gorrie said.
The couple had gone from spending thousands every week on drugs, to saving for Christmas, and starting a new future together.
After Miss Manning lost her sister Jasmine a few months beforehand to suicide, she started having "wonderful goals".
"We had plans to start our own family,'' Mr Gorrie said.
"You and your co-offenders took that from us - and for what? The promise of a patch.''
Mr Gorrie's mother, Frances, put it to Fawcett in the dock, that if he thought taking part in such a brutal killing, would make him a man, then he had a lot to learn.
"If you believe barking around a girl's beaten body and shouting Nazi slogans is manly, you are sadly mistaken,'' she said.
"Our European and Maori Battalion soldiers who fought against that very cause would be disgusted and ashamed of you.''
If Fawcett had "any guilt or feelings of horror" at what he had done, then maybe there was hope for him in the future, said Mrs Gorrie.
"It's never too late to change.''
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.
Outside court, Miss Manning's brother Rob welcomed the sentence, which was longer than he had expected.
"I was really, really happy with it,'' he said.
Justice Gendall spoke about the long lasting impact the violent murder has had on the Manning family - comments that Mr Manning appreciated.
"I think that is a really important message to get across as well - we're actually the victims now.
"It's hard sitting in there listening to it all.''
He says he feels some vindication for his sister today but knows that it's not over, with the police investigation still ongoing.
Mr Manning had faith that the others would be brought to justice.
Kent Gorrie, Miss Manning's former minder and partner, said he would not be happy until "the rest of them get charged''.
''[Police] know who they are. I can pretty much name them - I wouldn't, but he [Fawcett] has named them all,'' he said.
Fawcett needs to "man up'', Mr Gorrie said.
"He's the one who has to live with it now.
"He's in protection. He'll be in 24-hour lock-up for, what, the next 20 years, at least? And that's going to do anyone's head in.''
Life now is "lonely'', he said.
He misses her and she is never far from his mind.
Prostitutes' Collective Christchurch regional co-ordinator Anna Reed said 20 years was a "good sentence''.
"Very, very good police work got this case through. I sat through that trial and I was amazed at what they did.''
Detective Senior Sergeant Brian Archer today said the conviction and sentencing of Fawcett was "a significant step'' in the police investigation.
"There is, however, no dispute that other people were also involved in this murder, and police are continuing to actively pursue those individuals,'' he said.
Police are continuing to appeal for information.
Anyone with information is asked to contact Christchurch police on 03 363 7400, or anonymously via Crimestoppers on 0800 555 111.
