A Grain of Truth
It was an improbable discovery that finally led the police to Mellory Manning’s killer.
Part Four
By David Wolman
Illustrations by Cam Floyd
Two weeks after Mellory was murdered, a young detective named Gabriel Thompson had visited the Mongrel Mob warehouse on Galbraith to talk with any occupants. No one answered when she knocked on the door, so she turned to leave. That was when she noticed that some of the grasses in the vacant lot next door looked similar to some of the seed heads that had been plucked from Mellory’s coat. Williams took a few samples with her, just in case, and sent them on to Mildenhall.
The grasses were ripgut brome. Mildenhall gave them a look but found nothing out of the ordinary: pollen from the grass itself, as well as from other weeds commonly found in vacant lots in that part of the world.
Williams also asked Mildenhall to look at samples taken from the jacket and compare them with material from around the Mongrel Mob crib. He didn’t think it was a total waste of time, but the pollen was so widespread that its presence (or absence) couldn’t signify much of anything.
Yet when he examined sample BDX004, from Mellory’s coat, Mildenhall noticed something astonishing. Although pollen grains are dazzlingly diverse, they have some things in common: hard outer shell, reproductive cells, and a single pore. This pore is the hole through which the gametes — basically sperm — are carried outward to do their business.
Under the microscope, ripgut brome pollen is roughly spherical, like textbook drawings of single cells, with a distinctive smaller shape enclosed within: a pore. This particular grain, however, had not one but two pores. At first Mildenhall thought it was a trick of the eye, a lump, a bump, a dark spot that just looked like another pore.
But soon after, he saw a second one just like it. Then a bunch more. Now there was no mistaking it: Something like 5 percent of the ripgut brome pollen in the sample from Mellory’s coat contained two-pored grains — an unusual, unexpected mutation. “It was just incredible!” Mildenhall says. “Something must have changed it at the genetic level!”
To a pollen geek, this is dramatic in the same way that, say, a five-legged dog is dramatic. Mildenhall contacted Vaughn Bryant in Texas for a second opinion. Bryant took a look at the images and immediately e-mailed Mildenhall to confirm what the New Zealander already knew: It was mutant pollen, all right. If the cops could find matching samples from a location in Christchurch, they could potentially unlock the case.
Mildenhall believed the aberrant pollen grains had been caused by an herbicide. It was just a theory, but he thought a weed killer sprayed on grass just when it was going to flower could have caused the genetic mutation. He mentioned the idea to Williams. Could Mellory’s coat have come into contact with an area that had recently been sprayed?
Less than two weeks later, police confirmed that the vacant lot next to the warehouse had been sprayed with an herbicide just a month before the murder.
So Williams sent Mildenhall back to rework the samples taken from Galbraith Avenue, to specifically look for more mutant pollen. Finding some would all but confirm that the killing had happened there.
Mildenhall was dubious. “What were the odds I’d see it at this possible crime scene? I thought completely zero.” Zero because the pollen on the coat — whether it was mutant or normal — had come from just one or two plants. Zero because any signal from the parent plant would be swamped by pollen from other grasses and bushes in the area. Zero because ripgut brome releases pollen for only a short period each year, so there was no chance of capturing any more. And zero because of the rarity of two-pored pollen to begin with.
Mildenhall proceeded nevertheless — better to look for a needle in an epic haystack than watch another case go cold. “I was skeptical I’d find anything, but hoping like hell that I would.” He spent three days scrutinizing sixteen slides full of pollen grains taken from Galbraith Avenue. On the afternoon of the third day, he spotted one. “This was the jackpot!”
He immediately called Williams. The find was consequential, no question. But it was only a start. Mildenhall needed to find more, which he did. Still more mutant pollen on the coat would eventually seal it. The grains were so deeply embedded in the fabric that “direct and forcible contact” was the only explanation for how they had gotten there. Mellory had been on her back, partly on a pad of concrete, partly on the grass, struggling for her life. The police had their location.
On Mildenhall’s suggestion, the police asked a botanist to go to the site and check for other potential sources of two-pored pollen. There were none. Mildenhall triple-checked by looking again at samples from other locations around the city, to demonstrate that the two-pored grains had come from material outside the warehouse. Although it’s possible aberrant pollen could have come from other places, the numbers were just too unusual. In all of Mildenhall’s experience, and likewise that of other top palynologists he consulted, mutant grains in such concentration had never been seen.
When I asked if he missed the aberrant pollen the first time around, Mildenhall said no. “It was one of those truisms of science,” he said. “It’s much easier to find something once you know what you’re looking for.” When profiling samples, it’s a matter of identifying and counting grains to determine concentrations of various types. Once he had discovered the aberrant grains and discussed their possible significance with Williams, his mind and eyes shifted frequencies. The new search was literally more granular.
“The pollen evidence was a keystone,” Mildenhall says. Williams and his team were able to use the location specifics in conjunction with other information — river-flow tests, cell-phone data, witness accounts — to question suspects. Under questioning, a young member of the Mongrel Mob named Mauha Fawcett ended up revealing details he could have known only if he’d been part of the killing.
On a bright, windy afternoon last June, Mildenhall and I took a taxi from Christchurch International Airport to the neighborhood of Dallington. The magnitude-6.3 earthquake that struck Christchurch in 2011 devastated this part of the city, leaving thousands of homes uninhabitable because of the shifty ground. The neighborhood’s empty silence calls to mind a plague or zombie movie. Mildenhall could barely recognize the place.
After stopping at the site along the Avon where Mellory’s body had been found, we drove to Galbraith Avenue. On the way, we talked about earlier cases — about Kirsa Jensen and Kirsty Bentley. Both of those investigations are technically still open, but Mildenhall says they’ll never be solved. “At least that’s not Mellory’s story,” he says.
Last spring, Mauha Fawcett went on trial. Mildenhall’s testimony lasted two hours. Fawcett had chosen to represent himself, and when the opportunity arrived for him to cross-examine Mildenhall, Fawcett simply said: “I’m confused about this one. I might just pass.” The investigation itself is not yet over — Williams is tight-lipped about specifics, but it’s no secret that the police suspect other people were involved in Mellory’s death. Fawcett, for his part, was convicted of murder and sentenced to life in prison.
Mildenhall stepped out of the taxi at the location where the Mongrel Mob warehouse once stood. “They killed her here and probably carried her down Galbraith and dumped her in the river,” Mildenhall told me, pointing toward the Avon.
Many of the surrounding houses, although unoccupied, are still there, forming a perimeter around the gang property. I could see how easily weeds and grasses, the ones that ended up breaking the case, would have encroached on the yards of these homes.
We stepped through a gap in a temporary chain-link fence. Hands jammed in the pockets of his fleece sweatshirt, Mildenhall scanned the ground as he navigated rubble, weeds, and piles of dirt. At one point, he crouched and felt a browned, tired-looking grass that was about as high as his shin. “It’s not feathery enough to be ripgut brome,” he said.
As we searched the area, the palynologist was somber. He had finally helped solve a murder case on his own doorstep, yet the feeling was anything but triumphant: His one-in-a-million forensic revelation doesn’t matter to Mellory and can’t ease her family’s pain.
The murder site itself has completely disappeared, buried beneath mounds of debris and earth. “A final insult to her memory,” Mildenhall said, kicking a chunk of concrete. “You couldn’t even put flowers on the place if you wanted to.”
This story was written by David Wolman. It was edited by Bobbie Johnson, fact-checked by Eric Wuestewald, and copy-edited by Will Palmer. Illustrations by Cam Floyd for Matter.
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