Miss Manning's mutilated and partially-naked body was discovered floating in the Avon River the day after she was killed.
Dr Dallas Mildenhall, GNS principal scientist and forensic palynologist who is expert in pollen spores, was tasked with analysing pollen samples and relating her clothing to scenes of interest in Christchurch.
He was surprised to find on her hooded cardigan a "very rare" genetically-mutated two pored grass pollen.
Dr Mildenhall had never previously encountered it in his 45-year career. Three other highly experienced, and globally renowned colleagues, agreed it was a particularly rare find.
Further investigations found the exact same pollen at the Mongrel Mob ganghouse at 25 Galbraith Ave in Christchurch. Pollen only travels "a few metres from source", the court heard.
It was also found in the carpet, underlay and floor sweepings from under the gang pad building.
Given that the pollen wasn't found at any other scene of interest, and its "remarkable" rarity, Dr Mildenhall said "the evidence strongly suggests" Miss Manning came into contact with it at the gang pad.
That type of pollen was not found in her nasal passages.
And since it was found on the rear of her hood and left sleeve of the cardigan, it was likely Miss Manning was on her back when the pollen became attached, he said.
Dr Mildenhall went as far to say that "the evidence does not exclude the possibility" that Miss Manning took her last breath at the gang pad.
In his first police interviews, Fawcett described how Miss Manning was taken to the gang pad at Galbraith Avenue, Avonside, where she was raped, bashed and stabbed.
Fawcett initially told police that Mongrel Mob gangsters barked like dogs and gave Nazi salutes as they carried out the fatal assault. She was then dumped in the river 200 metres away.
Fawcett later backtracked from his earlier version of events, saying he wasn't present during the attack.
Under cross-examination by Fawcett's amicus curiae - lawyer Craig Ruane appointed to provide legal assistance - Dr Mildenhall today rubbished suggestions the rare grass could've come from another property.
"It's almost impossible," he said.
Justice David Gendall asked Fawcett if he had any questions.
"I'm just a bit shocked that it came from the one place... and not anywhere else in Christchurch," he replied.
"Is that a question you'd like to put to Dr Mildenhall," the judged asked Fawcett.
"Um, I don't know what to say, sir. I think I might just pass."
The trial has adjourned for the weekend and will resume on Monday.
