Force of nature

A powerful yet generally underutilised field of forensic science could now become more widely used in criminal investigations following new research that can “harness the power of pollen to solve crimes”. Palynology – the study of pollen – is traditionally used to date fossils, examine relationships between plants and learn about evolution by analysing layers of rock, although it has, on occasions, proved a vital factor in criminal analysis. Invisible to the naked eye, pollen is present in every environment, from grasslands and farms to city centres and beaches. Different species of plants thrive in different environments and flower at different times of the year, which means pollen grains can be used as a biomarker, linking a person to a specific time and place. In August 2012, Humberside Police confirmed it had solved a 28-year-old ‘cold case’ thanks to pollen spores linking the victim and his killer. Murdered Christopher Laverack was nine years old when he went missing from his home in March 1984. For years the case remained unsolved, but a breakthrough came in March 2002 when the boy’s uncle, Melvyn Read, was arrested for sexually assaulting four young boys who were known to him. Read was jailed for seven-and-a-half years in April 2003 and a police review of the unsolved murder showed a strong circumstantial case against him for the death of Christopher. He lived locally, owned a car which fitted the description of a vehicle seen near the victim’s house on the night, he did not have an alibi, had previous knowledge of the area where the body was dumped and was shown to have lied to police about key issues in the case. When historical DNA analysis drew a blank, Detective Superintendent Ray Higgins asked Dr Patricia Wiltshire, a renowned palynologist, to look at the case. Her report concluded there was enough “unusual pollen and other plant material” on the clothing Christopher was wearing when he was killed to link him to Read’s garden and that there was “scientific evidence to show that Christopher had been in close contact with Read’s garden the night he went missing”. Read died in prison in 2008, but an independent review of the evidence by a leading criminal QC concluded that, had Read been alive, the evidence would have led to a charge of murder and a realistic chance of conviction. In another case involving Dr Wiltshire, pollen traces proved a key strand of evidence linking a vehicle driven by Soham double-killer Ian Huntley to the place where his two young victims were buried. Forensic palynology has proved particularly useful in rape cases, for example where the defendant renders DNA evidence ‘redundant’ by claiming that the victim consented to sex, as pollen analysis can ‘confirm’ or ‘eliminate’ specific locations. In one case, a suspect claimed he and his victim had engaged in sex on a lawn behind a building while the victim said she had been attacked in a wooded area. As the suspect did not deny contact, he willingly surrendered the clothing he had been wearing at the time. Analysis of pollen samples clearly showed he had been in the woods rather than on a lawn. While this did not prove that he committed the crime, it proved that he had lied about his whereabouts and this was ultimately sufficient to prompt a full confession. Following the Bosnian War, investigators uncovered mass graves of bodies that had been killed elsewhere and buried temporarily before being moved. Traces of pollen on the corpses provided vital evidence in identifying the original burial sites and those responsible for the deaths. In a case in New Zealand, a burglar was tracked to the scene of the crime when pollen grains on his clothing were matched to a rare plant growing in front of the victim’s house. Forensic palynology typically involves identifying pollen grains under a powerful microscope. This is a highly-specialised skill with only a handful of experts across the world, such as Dr Wiltshire, able to identify a plant based purely on the size, shape and colour of its pollen grains.