The top slab was very heavy and required several people with strong arms and good backs to move it. The void within was bare and covered in decades-old aggregations of spiders’ webs and the odd leaf that had somehow worked its way in through a crack. The floor was covered with daylight- and water-deprived crumbly soil. It had not been touched for many years. We sighed in disappointment, completed our notes and headed off to the next grave. One by one, we went through a similar process until we reached the end of our list. We found nothing. Failure.
Failure is such a harsh word, but we must live with it. Very often, my colleagues and I fail. It can be very hard to find a person and most searches end in failure. I know that the police have since searched other locations in the area, and as yet they have not found the victim of the gangland beating that turned to murder. Everyone working as part of a criminal investigation must brace themselves for failure. Whilst the phrase ‘cold-case’ elicits a frisson of glamour and excitement in the public, it simply means that we have failed, so far. Famous long-standing cases such as the disappearance and probable murder of the estate agent Suzy Lamplugh on the 28th July 1986 from outside a flat in Fulham in south-west London have fascinated the public but have caused immense pain to the living. Nearly 25 years after Suzy’s disappearance police received information about a possible burial site near Pershore, Worcestershire. A witness recalled that they had seen a suspicious mound in the field around the time of Suzy’s disappearance. The field was several miles from an abandoned military barracks which were searched in 2000 and 2001 following reports that the main suspect, John Cannan, had buried Suzy’s body there. Despite searches using ground penetrating radar and the skills of two scientific specialists, nothing was found.
Finding a murder victim is often a very, very complex business. Get one element wrong and the chances of success dwindle rapidly. An obvious example of this is the dependence upon witnesses. Often these may be the perpetrator or their associates. It is usually not in their best interests to tell the truth and lead the investigating team to their victim. No matter how good the technology or the experience of the investigating scientists, if the intelligence is wrong or misleading then there is a lower chance of recovering someone’s remains. But even a failure is some sort of result. Unless we have missed them, we can confirm that the victim is not at that location. And so, the search continues …
8
Pollen and Spores
Within popular TV dramas and novels, the presence of plant pollen on a suspect’s clothing is often used as a way of connecting them to a victim or a crime scene. Of course, it’s not always as simple as that; pollen has its strengths and weaknesses in the forensic environment. To understand these strengths and weaknesses, it is necessary to learn a little about what pollen is and how it works. Pollen is a word that many of us are familiar with, especially those with allergies such as hay-fever. Even so, most people are probably unaware of how important pollen is. Without it, our world would grind to a halt. Most plants on the planet are dependent upon it for reproduction, this is because pollen is the plant equivalent of sperm. Without pollen, the embryos in flowers will go unfertilised and there will be no seed and therefore no more plants, animals, food or people. From an allergy point of view, most plant pollens don’t contribute to hay-fever. Generally speaking, plants with wind-pollinated flowers, such as grasses and some trees, tend to cause hay-fever and those that are pollinated by animals such as insects or birds, don’t. How do you tell which is which? The wind does not have eyes, and so the flowers don’t need to attract it. Therefore, the flowers of wind-pollinated plants are small and usually green. To most human eyes, they tend to merge with the leaves. Flowers pollinated by animals need to attract the animals and they do this either by scent (which we may or may not be able to detect) or bright colours.
Pollen and plant spore (some plants, such as ferns, have spores, not pollen) cells often have tough outer coatings which mean they can persist for a long time. Under the right environmental conditions, pollen grains can last in soil for thousands of years. The toughness of pollen and plant spores is down to the composition of the cell walls. The outer cell wall of pollen is largely made of sporopollenin, one of the most robust and chemically inert naturally occurring biological polymers. Because of this durability, their presence in ancient soils is one of the ways that scientists can reconstruct past climates. As the climate changes, the plant communities change and so does the pollen profile.
This persistence in the environment is the key to pollen’s usefulness in forensics. The presence of pollen on a person’s clothing or footwear can be used to link them to a specific location. How is this done? All plants have specific needs − some like nutrient-rich soil, others require plentiful sunshine. This means that plants are restricted to particular types of environment, or ‘habitats’ as they are referred to in biology. Familiar habitat types found in north-west Europe include woodlands, sea cliffs or chalk grasslands. On top of this, very few plants have a global range and even in Britain and Ireland there are not many plants that are found everywhere. These factors mean that many plants have distinct distribution patterns across our land. It is these distribution patterns that are the key to using pollen in forensics.
Pollen is a valuable tool, but it has some limitations. The pollen of plants that rely on the wind tends to be more widely dispersed in the landscape. Pollen from wind-pollinated trees like oak (Quercus), beech (Fagus) or birch (Betula) can be blown many miles. This can reduce the value of some types of tree pollen in forensics. But, a high abundance of oak, beech and birch pollen on a suspect’s footwear will strongly indicate that they have been in or near a woodland or wooded park. However, these pollen types won’t help an investigator locate where exactly in the wood or park the suspect has been. Also, the pollen of some wind-pollinated plants, such as grasses, can be quite hard to identify accurately. The reason for this is their need to be buoyant and aerodynamic; objects with sculpted, sharp-angled surfaces don’t fly very well. This need for buoyancy results in pollen grains that have relatively few surface features, a bit like car air-bags. However, some windborne pollen types are quite distinctive; the pollen of pine trees (Pinus) was described to me and my fellow undergraduates as looking like Mickey Mouse’s head in outline. The pollen grains of pines have two inflated ‘ears’ either side of the ‘head’. The ‘ears’ help the pollen float in the air. On the other hand, the pollen of plants designed to attract the attention of animals like bats, birds and insects tends to be heavier and have ornately sculpted surfaces. The surface sculpting helps the grains stick together as well as to the animal that will transport the pollen to the next flower. Unlike wind-pollinated plants, the ‘wasted’ pollen of these plants tends to fall to the ground near the plant it came from. Also, the surface ornamentation is incredibly diverse (and very beautiful) in these plants, so much so that in many cases they are unique to individual plant species.
All the above means that it is possible to create a pollen profile that can be used to link a suspect to a specific location. A pollen profile containing widespread woodland trees like oak, beech and birch can be useful but what really helps is if there something a bit more interesting. If I were lucky enough to be looking at a pollen profile that contained the aforementioned trees, as well as the pollen of plants like honeysuckle (Lonicera periclymenum), ramsons (Allium ursinum), wood anemone (Anemone nemorosa) and yellow archangel (Lamium galeobdolon), I’d be really chuffed. This list would tell me straight away, that not only was the location woodland but that it was ancient woodland. This is, as you can imagine, old woodland, and by old in England and Wales we mean at least 400 years old. Not only are ancient woods old, they also tend to have lots of plant species within them, such as the plants above, and these plants are often known as ‘indicator species’ because they are strongly associated with particular habitat.
Ancient woodlands are old, species rich and pretty scarce. They are scarce because our ancestors cut down much of our
woodland for agriculture, charcoal and timber for building houses and ships and in the last 200 years we destroyed more by building railways, cities and motorways. Nowadays only about two percent of our landscape is covered by ancient
While I’d be very happy with the preceding list, what I’d really need to make my heart go aflutter would be a true woodland specialist and rarity. Something like spiked rampion (Phyteuma spicatum), a relative of the garden bellflowers (Campanula spp.) and now very rare in England and found in fewer than ten sites. Extracting spiked rampion pollen from an exhibit would lead me to be searching the woods around Hailsham and Heathfield in East Sussex. Clearly, this example is somewhat idealised, but the underlying principal is apparent: pollen can be used to link suspects to crime scenes.
Even after death, biological material such as pollen can remain lodged on and in our bodies. Forensic researchers sometimes come up with innovative means of retrieving information. One approach is to explore the nasal cavity. We may grumble about snot when we have a cold or hay-fever, but mucus is an amazing and important substance. Far from being simply snot, mucus is a complex substance made up of salts, enzymes, antibodies and other proteins. Most of our mucus is produced in our digestive tract where it helps protect the lining from physical damage and reduces potential harmful impacts of some bacteria. It is also found in our lungs and airways. Importantly this mucus traps small particles that we may breathe in, especially viruses, fungal spores, bacteria and pollen. Not only does mucus protect us but it is a snapshot of the environment we have been in. Anyone visiting or living in our more polluted, larger cities will attest this, as a walk along any main road is likely to result in black bogeys. The inner parts of the nasal cavity are complex and very narrow in places. Gaining access to these can be challenging. To do this, it is necessary to remove the facial skin and scalp, after which the upper portion of the skull cavity is removed. The exposed areas of the inner nasal cavity are then washed, and the liquid collected. The liquid is spun in a centrifuge to concentrate the particles and the concentrated material is then mounted onto a slide and examined under a microscope. The pollen and spores can then be identified.
Several years ago, I worked on the case of a woman who had gone missing some weeks earlier. The police had a suspect − her husband. They had searched the family home and had retrieved several items including outdoor clothing, footwear and a spade. They had also searched his car and recovered further exhibits. The police also had automatic number plate recognition (ANPR) data showing that, shortly after the wife went missing, his vehicle left the rural family home and was driven for about 100 miles. The distance travelled covered at least 2 counties. The police believed it was possible that he could have left the route at one of many different points and disposed of her body.
The police sent environmental samples taken from the exhibits for analysis to several specialists. I received some vegetation fragments that proved to be inconclusive, because the fragments came from widespread lawn grasses and were unlikely, on their own, to be of significance. The soil analyses provided some fascinating information. The soil was rich in hydrocarbons. The high levels of hydrocarbons, which were associated with exhaust fumes, indicated that the vehicle had travelled through a built-up, urban location. There were also chemical traces of an unusual industrial process that was of a very limited extent in the region. In soil retrieved from some of the exhibits, pollen and spores were also recovered and identified. Most of these were of widespread grassland plants and some more common trees. There was one spore type that was particularly interesting. It was the spore of a fern that is fairly common nationally; however in the two counties in question, the plant is rare and is only found in few restricted lowland areas. Basically, across these two largely rural counties we needed to focus our efforts on areas that matched our observations. The probable deposition scene was likely to be near an open grassy habitat close to a built-up area that was associated with an unusual industrial process. In the vicinity, there would be plants of the scarce fern. The environmental information had reduced the search area from several hundred square miles to fewer than 20. My fellow scientists and I were rather chuffed with the work and were keen to pursue it further. Inexplicably, the police did not pursue this area of work and as far as I know the case remains open. Typically, after our work is done, we hear no more.
Generally, the public perception of forensic science is coloured by ‘Grissom syndrome’, so-called by me in honour of the character Gil Grissom from CSI: Crime Scene Investigation. Because of the way popular dramas are structured, investigators and specialists are portrayed as multi-skilled super-heroes. Every now and then, when it plays a major role in a murder inquiry, real botany and forensic science captures our collective attention. Sometime after I joined the Natural History Museum, a young woman, Joanne Nelson, went missing on Valentine’s Day 2005. Shortly after her disappearance, her boyfriend, Paul Dyson, was charged with her murder. After a long search hampered by winter snow and cold, the police were obliged to scale down the operation. Dyson had confessed to disposing of Joanne’s body, but he claimed to be unable to recall exactly where. He told the police that he’d placed her body in bin bags and then driven from Hull towards York and dumped her by a metal gate with green bottles attached.
Despite driving around large areas of east and north Yorkshire with Dyson, the police were unable to find Joanne. Examination of Dyson’s clothing by a forensic botanist revealed an interesting pollen profile. Some of the pollen was of a non-native tree with a patchy distribution in England. This is the sort of botanical clue that people like me dream of − something uncommon that is large and stands out in the landscape. The pollen of the tree, western hemlock (Tsuga heterophylla), was found with pollen of birch, pine (Pinus) and the spores of polypody fern (Polypodium spp.).
At this point, the police team and the forensic botanist needed to enlist the help of amateurs. The word amateur often has connotations of unskilled or inexpert. Not in this case. The amateurs the team needed the help of were members of the Botanical Society of the British Isles (now called the Botanical Society of Britain and Ireland). The BSBI is one of the oldest natural history organisations in the world, whose roots go back to 1836. It is an organisation of committed and expert people who know the wild plants of these islands better than most. Much of what we know about our wild plant life is based on BSBI expertise. Indeed, various parts of our economy are driven in part by this knowledge – agriculture, conservation, national parks and planning decisions all have BSBI expertise embedded within. In a system devised by a man called Hewett Cottrell Watson in 1852, every area of Britain and Ireland has a person, the vice-county recorder, who is responsible for collating and verifying information on the native and nonnative wild plants of that area. I am recorder for vc 21, the historic county of Middlesex. The biggest English county, Yorkshire is so large that it is broken up into five vice-counties.
One of the things we recorders do is compile botanical records and maps and it was botanical maps compiled by the BSBI that enabled the investigating team to narrow their search. These maps showed that western hemlock was restricted to a few locations in that part of Yorkshire. A few days after focusing the search around the map, Detective Superintendent Ray Higgins, who was leading the investigation, was driving to meet one of the search teams near Brandsby, when he and Detective Constable Phil Gadd saw the gate as described by Dyson. Later, when being interviewed by reporters, Higgins described how they ‘were driving round and saw this gate – it had everything. We looked at each other and said, ‘This is it.’ A path from the gate, surrounded with green bottles, led into a wooded area.’ The officers stopped the car and, after a brief search in the wood, they found the partially uncovered remains of Joanne. The investigation was a success, and Dyson was found guilty. The discovery of Joanne Nelson’s body might not have happened for many years without the expertise of trained and experienced botanists working alongside the detectives, particularly as Brandsby is not be
tween Hull and York where the original search was concentrated.
9
Looking Anew
The interest of us botanists, like other human beings, is often aroused by the beautiful or the rare. We can tend to be less interested in the mundane or commonplace. Most of us would rather be looking at ancient chalk grassland full of orchids instead of nettles covered in vomit and urine in an alleyway by a mortuary. Surprisingly, this particular alleyway is one of my favourite botanical sites in London; it’s fair to say that my interest in urban botany and forensics has rather warped what I find interesting! The nettle here is no ordinary nettle, it is membranous nettle (Urtica membranacea), a recently and accidentally introduced non-native species from the Mediterranean region. It arrived on these shores as seed in the soil of large container-grown plants imported from southern Europe. Owing to all nettles’ proclivity towards nitrogen-rich environments, the plant was very much at home amongst the pigeon poo and puke. These effluvia from the bodies of animals are very rich in nitrogen. My years botanising in London have primed me to look at wild plants very differently to how I otherwise would have done, a way that would help me greatly in later years when I started doing crime-scene work.
After completing my PhD at the University of Reading in 2002, I started volunteering at a local nature reserve in central London. Camley Street Natural Park is an important site, a tiny fragment of the natural world in the midst of the glamourous, people-centric and nature-blind redevelopment of the King’s Cross area. Camley Street taught me a lot. Even though I had lived in London for most of the previous decade, I’d rarely paid attention to its natural environment, mainly because I’d become involved in the gay scene and activism. The park was managed by the London Wildlife Trust and later, when I needed a job, my time volunteering at Camley Street proved invaluable. The London Wildlife Trust, on behalf of the Great London Authority, needed botanists to travel around London doing surveys of all the public space they could access. For two years I cycled across miles of London documenting, mapping and learning about its wildlife, landscape and history. I recorded the plant life, and the presence of amenities, bins or excessive dog-fouling, with the intention of documenting the often negative changes that had occurred. Many of London’s biologically diverse brownfield (former industrial) sites have been lost to development while others are becoming smothered by invasive non-native species.
Murder Most Florid Page 10