How tiny pollen grains help solve brutal murders: The fascinating science behind nature’s invisible crime scene evidence
Bloodstains, fingerprints and weapons aren’t the only evidence investigators look for at crime scenes; pollen is another. Pollen grains are among the pieces of evidence that have helped solve some of the most high-profile murder cases in recent years, one grain at a time. Tiny particles invisible to the naked eye actually sparkle, revealing a lot to experts.
A murder was solved using pollen
In 2014, gang member Mauha Huataki Fawcett was convicted of Manning’s murder and sentenced to life in prison.
In 2008, Mellory Manning, a 27-year-old woman, was attacked and murdered while working as a prostitute in Christchurch, New Zealand. Police investigated and interviewed hundreds of people, but months later, they still lacked leads. They found an unusual expert, Dallas Mildenhall, a white-haired scientist in his 70s who worked as a forensic palynologist, pollen and spore expert, and had helped solve many murders around the world.One of the main reasons the investigation has floundered is that police have been unable to reveal where the woman was killed. “They had long been very suspicious of a gang called the Mongrel Mob because they were involved in prostitution and they had this kind of warehouse hangout not far from where the bodies were found. But they had no evidence of that connection. All they had were assumptions,” David Wolman wrote in Matter magazine. Mildenhall collected pollen samples from Melory’s nasal passages and clothing and began studying them.He is examining a type of pollen grain that usually contains only one pore. But Mildenhall “noticed that one pollen grain looked like it had two pores.” Mildenhall examined pollen collected from Manning’s body and noticed multiple examples of these highly unusual two-hole pollen grains. He shared his theory with police: An herbicide caused the pollen to mutate, giving it multiple pores.Sure enough, at this time of year, the area next to the Mongrel Mob hangout and the warehouse was sprayed. Police asked Mildenhall to re-examine pollen samples collected from the gang’s warehouse, where he eventually found high concentrations of the two-hole pollen grains. In 2014, gang member Mauha Huataki Fawcett was convicted of Manning’s murder and sentenced to life in prison.
Pollen: Silent and granular evidence
To biologists, pollen is evidence that helps catch thieves and murderers.
Pollen plays a vital role in solving crimes. For most people, pollen is the yellow stuff that bees collect, or the material plants need to fertilize and produce the food we eat. Others end up hating pollen because it can cause allergies. But to biologists, pollen is evidence that helps catch thieves and murderers.The technology of using pollen as evidence is relatively new. It was first used in 1959 to solve a murder in Austria. While countries like New Zealand have been using it for decades, now countries like the UK, Australia, Canada and the US are also using it.
But why is pollen such a good forensic secret?
Many types of pollen- and spore-producing plants spread large amounts of these palynomorphs into the air. Once in the air, they are carried by air currents and eventually fall to the ground in a thin coating called pollen rain. In some areas, the amount of pollen and spores spread is so great that bare land or water turns yellow. This coating is a snapshot of the area and becomes its “pollen print”. They can be used to identify and locate an area, as was the case with the Manning murders.Since most pollen and spores are tiny in size and can become trapped on any type of surface, they remain invisible to humans. Pollen is also resistant to decomposition because the cell wall is composed of cellulose and spore pollen, one of the most chemically resistant organic molecules known. A person does not know how much pollen is on clothing, so it is impossible for them to remove evidence of pollen from clothing and items.Forensic palynologists can identify the origin of pollen or spores found at a crime scene or on a criminal and use it as evidence linking a suspect or object to the crime scene. There are nearly half a million different plant species that produce pollen or spores, and each can be identified as coming from a parent plant. While some can be identified with a simple microscope, others require special tools such as an electron microscope (SEM) or a transmission electron microscope (TEM), according to Arizona State University.But this evidence is not being used more frequently. This is because, like other forensic evidence, it can be difficult for judges and juries to understand. Furthermore, studying pollen grains, like two-pore pollen, is a difficult and time-consuming task for scientists with expertise rare in the world.
