Solving Crimes With Pollen, One Grain Of Evidence At A Time

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Dallas Mildenhall, New Zealand's forensic pollen expert, peers at samples through a microscope. (Courtesy of David Wolman)
Dallas Mildenhall, New Zealand's forensic pollen expert, peers at samples through a microscope. (Courtesy of David Wolman)

Some murder cases are harder to solve than others. The investigation into the killing of Mellory Manning — a 27-year-old woman who was assaulted and murdered in 2008 while working as a prostitute in Christchurch, New Zealand — confounded police.

They conducted an investigation and interviewed hundreds of people, but months later, they still had no solid leads.

To crack the case, the police required the expertise of an unusual specialist. Dallas Mildenhall, a white-haired scientist in his 70s, is a forensic palynologist – a pollen and spores expert who helps solve crimes. One of only a handful of such experts in the world, he has helped solve cases of murder, arson and art forgery all over the globe. He once traced counterfeit malaria drugs to the border of China and Vietnam by identifying pollen in the capsules.

Police turned to Mildenhall, who lives in Christchurch, when their investigation into the Manning case got stuck.

"One of the major reasons why [the investigation] was stuck is that the police could not say for sure where she had been killed," David Wolman, who wrote about the case for Matter magazine, tells NPR's Arun Rath. "They were very suspicious early on of a gang called the Mongrel Mob because they were involved in prostitution — they had this sort of warehouse hangout not far from where the body was found. And yet they didn't have the evidence making that connection. All they had was supposition.

"So the challenge for someone like Mildenhall, then, is to come in and look at pollen samples taken from Mellory's nasal passages and her clothing and try and link it to locations that the police are wondering about as far as potential scenes for the crime."

A single pollen grain from a sample tells you nothing. But together, all the pollen grains in a sample — their composition and concentration — can reveal a lot. Still, we're talking about pollen grains, their details invisible to the naked eye.

Mildenhall examined pollen from potential crime scenes around Christchurch, but came up with nothing. Then, after months of peering through the microscope at tiny slides, he saw something almost unbelievable.

He was examining a kind of pollen grain that normally contain only a single pore. But Mildenhall "noticed a pollen grain that looked like it had two pores," says Wolman. "It really doesn't sound that exciting ... and at first, he thought it was just a trick of the microscope or a sample maybe had been smushed or deformed — because to get a sense of how rare it was, how dramatic this finding was, he said it would be like seeing a dog with five legs."

Mildenhall examined the pollen taken from Manning's corpse and noted multiple examples of these highly unusual, two-pored pollen grains. He shared his theory with the police: An herbicide had caused a mutation in the pollen, giving it more than one pore.

"Sure enough," says Wolman, "the area right next to the Mongrel Mob hangout and warehouse had been sprayed precisely at the time of year that Mildenhall suspected."

The police told Mildenhall to reexamine pollen samples collected from the gang's warehouse. "And so he spent three days poring over these samples again," Wolman says. "And then, lo and behold, he started to find significant concentrations of this two-pored pollen grain."

That clinched it. The pollen embedded in Mellory Manning's clothing during her murder was solidly linked to the Mongrel Mob's hangout. Police interrogated a suspect and presented him with this forensic evidence, "saying, 'Look, we can connect you to this place at that time of year,' and that rattled him enough that then he started to sing," Wolman says.

Last year, gang member Mauha Huataki Fawcett was convicted of Manning's murder and sentenced to life in prison.

If pollen can play a crucial part in solving a case like this, why isn't it used more often? Wolman says that like much forensic evidence, it can be hard for judges and juries to understand. But studying it is also difficult, time-consuming work — and scientists who have this expertise are about as rare in the world as two-pored pollen. And there may be no one who sees the world like Dallas Mildenhall.

"Dallas Mildenhall is a guy who, he doesn't look through the air at the landscapes in front of him," Wolman says. "He sees this blizzard of activity in the world around us, constantly, of pollen grains swirling and storming and rising and falling and raining down on the ground. The trick is being able to read that rain."

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Transcript

ARUN RATH, HOST:

Recently, I talked with a reporter named David Wolman, who told me one of the weirdest crime mysteries I'd ever heard - a case unlike anything in the history of forensics. It begins with the murder of a troubled young woman named Mellory Manning.

DAVID WOLMAN: Mellory Manning grew up in Christchurch, New Zealand. Mellory had a drug problem. She was working as a prostitute. And after her sister killed herself, Mellory realized that her life was headed down a similar path. So she was starting to turn things around, but unfortunately, the Christmas holiday was coming up, and she felt like she needed more money. And so she decided to work the street one last night. It was that night, in December of 2008, when she was murdered.

RATH: Mellory Manning's murder confounded the police. Despite a massive forensic investigation and hundreds of interviews, they went months without a solid lead. Then a 70-something scientist named Dallas Mildenhall came to work on the case.

WOLMAN: He's a kiwi, and he has this thinning shock of white hair and bulging blue eyes. And Dallas Mildenhall is a forensic palynologist. And that is not a term I had ever heard of before learning about him. He is basically a pollen and spores expert who brings to bear his expertise on criminal investigations.

RATH: What you need to know about Dallas Mildenhall is that he's one of only a handful of forensic palynologists in existence. He's aided investigations all over the world, using pollen to connect the dots in murder, arson, even art forgery cases. He once traced counterfeit malaria drugs to the border of China and Vietnam from the pollen grains in the capsules. So when the Mellory Manning investigation hit a wall - in his home country no less - the pollen detective gets a call.

WOLMAN: One of the major reasons why it was stuck is the police could not say for sure where she had been killed. They were very suspicious early on of a gang called the Mongrel Mob because they were involved in prostitution. They had this sort of warehouse hangout not far from where the body was found. And yet they didn't have the evidence making that connection. All they had was supposition. So the challenge for someone like Mildenhall, then, is to come in and look at pollen samples taken from Mellory's nasal passages and her clothing and try and link it to locations that the police are wondering about as far as potential scenes for the crime.

RATH: A single pollen grain from a sample tells you nothing. But all the pollen grains in a sample - their composition, their concentration, all that stuff - can tell you a lot. Still, we're talking about pollen grains in detail invisible to the naked eye - painstaking work. For many months, Mildenhall examined pollen from lots of potential crime scenes around Christchurch and came up with nothing. Then, after months of peering through the microscope at tiny slides - something almost unbelievable.

WOLMAN: So what happened to Mildenhall one day is that he noticed a pollen grain that looked like it had two pores. It really doesn't sound that exciting. Two pores - when I heard it at first, not being a scientist, I was, like, and? What does that actually mean? And at first, he thought it was just a trick of the microscope or a sample maybe had been smushed or deformed because to get a sense of how rare it was, how to dramatic this finding was, he said it would be like seeing a dog with five legs.

(SOUNDBITE OF MUSIC)

RATH: He looked at the pollen taken from Mellory Manning and saw multiple examples of these mutated pollen grains. How could that be? He has a theory - an herbicide has mutated the pollen, giving it two pores. He tells the cops.

WOLMAN: Sure enough, the area right next to the Mongrel Mob hangout and warehouse had been sprayed precisely at the time of year that Mildenhall suspected.

RATH: The police told him to re-examine the samples collected from the gang's warehouse.

WOLMAN: And so he spent three days pouring over these samples again. And then, lo and behold, he started to find significant concentrations of this two-pored pollen grain.

RATH: They had it. The pollen that was embedded in Mellory Manning's sweater during her murder was solidly linked to the Mongrel Mob's hangout.

WOLMAN: Then what happened is, while interrogating a suspect, they presented this forensic evidence to him, saying, look, we can connect you to this place at that time of year. And that rattled him enough that then he started to sing.

RATH: That man is convicted of the murder of Mellory Manning and sentenced to life in prison. So if pollen can play a crucial part in solving a case like this, why isn't everyone using it? Well, two things - David Wolman says that like lots of forensic evidence, this is really hard for judges and juries to understand. But it's also difficult, time-consuming work, and there are only a handful of people in this field worldwide. And there may be no one who sees the world like Dallas Mildenhall.

(SOUNDBITE OF MUSIC)

WOLMAN: Dallas Mildenhall is a guy who - he doesn't look through the air at the landscapes in front of him. He sees this blizzard of activity in the world around us, constantly, of pollen grains swirling and storming and rising and falling and raining down on the ground. The trick is being able to read that rain.

(SOUNDBITE OF MUSIC)

RATH: You can read David Wolman's fascinating piece "Who Killed Mellory Manning?" in the online magazine Matter. Transcript provided by NPR, Copyright NPR.