Traces

by Patricia Wiltshire

  The robustness of those pollen grains had to be an advantage in my attempts to get them out of the fabric. One answer was to try to dissolve the garment in strong acids, leaving the more robust pollen grains and plant spores behind. This might have worked on cotton, linen or any other natural plant fibre – even if it were reconstituted, such as rayon or viscose – but it would not have been effective on synthetic fabrics such as acrylic, nylon, or polyester, which are manufactured from the by-products of the oil and coal industry. The jacket was made of some fleecy material, effectively from recycled plastic bottles, and I was pretty sure that I could not dissolve it away. In any case, it would have been an horrendous job and, with that amount of fabric, virtually impossible, as well as prohibitively expensive. No, there had to be another answer.

  When I found it, it had been staring me in the face. I had spent much of my working life in laboratories, but I did not find my answer there. I might have been a scientist, but I was a housewife as well, and once upon a time I had been a mother. I certainly knew how to get dirt out of clothes. One needs a surfactant such as detergent, which lowers the surface tension of the water so that it can penetrate and lift and flush away embedded dirt and particulates. So what is the difference here? It seemed so incredibly obvious. This was exactly what happened in my washing machine every time I used it.

  Perhaps you have heard of the principle of ‘Occam’s razor’. Well, this was a perfect example of it coming to life. William of Ockham (1287–1347) was a Franciscan scholar who favoured ‘the law of parsimony’. He said that, when we solve problems, the simplest solution is often the right one. Aristotle had had the same idea, many centuries before, and it is certainly a useful one in science, especially when grappling with complex scenarios and multiple possibilities.

  Detergent seemed the simplest solution, so detergent is what I used. I was worried that, when wetted, microbial activity might be stimulated in the fabric and pollen might start to decompose, so I needed some kind of disinfectant. Again, I was worried that the ones we use domestically might affect the palynomorphs. I needed something gentle, something that would not oxidise the palynomorphs; how about medicated shampoo? First of all, I needed to check that medicated shampoo did not contain pollen grains. It was highly unlikely but I had never looked, and I doubt if anyone else had done so either. I found it was sterile of anything, and so I had a good surfactant and a disinfectant in one. As I was to later discover when dealing with samples from decomposing corpses, the use of medicated shampoo had an extra bonus. It sterilised samples contaminated with bacteria and, in the process, removed the sickening smells as well. What a wonderful product for the forensic palynologist.

  I bought some new stainless steel bowls and sterilised them with neat bleach. This oxidises away many organic molecules, as well as bacteria and fungi – and, by the way, the tannin coating in your teapot. I then used the minimum amount of very hot deionised water which, although supposedly sterile, would need to be tested for pollen contamination. With dilute shampoo, I worked away like a washerwoman. I agitated, rubbed, and rinsed each part of the garment, finally flushing it through with deionised water. This was certainly not rocket science, but I could not think of a better method.

  Each sample resulted in a grey, murky suspension. It was interesting to see how dirty this seemingly clean jacket had been in reality. By the end of my work, I had five samples – two fronts, two sleeves, and the back of the jacket – to compare against the ten samples I had taken from the flower bed, five of foliage and five of soil. I washed the leaves just as I had washed the fabric of the jacket. After processing, I made the microscope preparations and could not resist just quickly scanning each one to see what they were like. My extraction by washing had certainly worked well, and the preparations were rich in palynomorphs. Within a few minutes of these cursory scans, I knew the answer to the case. But scanning results would not be adequate for presentation to the court, and the tedium of identifying and detailed counting everything I saw was essential.

  When starting analysis of a slide, I always start my first transect at the left-hand top of the slide, slowly passing down to the left-hand bottom, viewing continuously under the microscope, stopping only to adjust to a higher magnification for more definite identification. This needs immersion of the lens in oil, and the use of phase contrast settings on the microscope. If any pollen grain were not easily identified, its coordinates on the slide were noted so that later I could scrutinise it more closely with the aid of my extensive collection of pollen reference slides. So, from the top edge, down to the bottom, moving over to the next field of view, then back to the top to start the examination of the next transect, repeating this over and over, covering as much of the slide as possible to remove sampling bias.

  In archaeology, as in forensics, this is a painstaking business. I have lost hours, days, weeks of my life to the microscope. The concentration it demands is immense; everything seen must be considered and catalogued, whether it is a pollen grain, fungal spore, fossil spore, or other microscopic organism. Focusing so intently on such tiny things is its own form of exquisite torture. Sometimes it can take an age before you start to build up a mental picture of a place. You are looking for patterns, concentrations of one plant’s pollen or concentrations of the next. But today a quick scan of the slides, before any real counting could begin, suggested exactly the assemblage I was looking for: rose pollen, each one with three deep furrows curving from the poles to the equator where bulging pores were situated, and lime pollen, so utterly easy to identify. It is flattened pole to pole and has three inverted pores around its equator, the outer wall decorated with tiny craters. This grain is a favourite of students just starting out in palynology because it is so easy to recognise.

  Another palynologist might have looked at the amount of lime and rose pollen on my slides and deduced that it was not enough to make any conclusions – but this only emphasised, to me, how little rose and lime shed into what we call the ‘pollen rain’, the pollen and spores that fall from the air.

  The proportion of rose pollen in the flower bed was 10%, and on the jacket front was 7%; for lime the result was 18% to 15%. The percentages were close enough to convince me. The likelihood of picking up that amount of these taxa without direct contact was infinitesimally small. The very small amounts of rose and lime pollen retrieved from the flower bed simply demonstrated how little pollen these plants released from their flowers. The rest of the pollen profile on the garment and in the flower bed was quite diverse, but interestingly, the same assemblage of taxa was present in each.

  It was intriguing that there was no rose or lime pollen on the toes of the boy’s shoes, nor indeed much of anything else. Then I thought back to that place. The flower bed was so small that his feet had remained on the paving slabs surrounding the bed, and he would not have picked up much from those slabs.

  The back of the jacket yielded very few pollen grains, and no rose or lime were found. It seemed clear to me, then, that the back of the jacket had not contacted the flower bed as the front had done. It proved to be a good control because it demonstrated clearly that any pollen coming from the air, or other sources, was very sparse and, indeed, did not match the flower bed. In my view, there was a high likelihood that the jacket front and the elbows had been in contact with the foliage and soil in the flower bed.

  The boy was lying – the girl had certainly not scratched her own skin in order to claim rape falsely. False claims of rape do happen occasionally, and I have saved one or two young men from jail with similar kinds of analysis to the first of my cases.

  Building up a reference collection in my early palynology days was a happy time. It involved gathering flowers in the field, accurate identification, and visits to herbaria and museums if they were generous enough to give me a few anthers from specimens. My reference collection is so very precious, and I would feel insecure without it. Indeed, one never stops collecting and comparing. The process of identifying and counting ea
ch pollen type in each sample is mind-blowingly tedious, although moments of excitement come when unusual pollen or spores are found. The ones I hate most are the small, oval-shaped ones, with three furrows and a fine network across the surface of the grain. They are the pollen equivalents, or almost, of difficult groups of plants like blackberry or dandelion, where tiny groups of specialists are the only ones who can name them confidently – or the LBJs (little brown jobs, as my husband calls them), small brown fungi with few distinguishing features.

  It is also difficult knowing when one has counted sufficient pollen to make a case. Sometimes, one can produce evidence from relatively few, and other times one might have to count thousands. A textbook needs to be written about these problems and, perhaps one day – who knows? After the enforced but, in reality, unnecessary counting of samples from this boy’s clothes, I calculated the relative frequencies of various pollen and spore taxa, drew up some bar charts to help the police understand what I was getting at, and they passed them to the Crown Prosecution Service and the boy’s defence barrister.

  His barrister must have sat him down with his parents and solicitor and showed him my diagrams and tables of figures, with accompanying explanations. He must have been stunned that his jacket had revealed the truth about his attack, and he reluctantly confessed. The girl was spared the agony of being put in the witness box in a court of law and having to relive that night under the scrutinising eyes of the jury, the public, and the press. The testimony of the thorny rose and lime trees in the square saved her that ordeal.

  What I had done was so simple – soil and dirt, a dash of medicated shampoo, a few inventive ideas, and a healthy dose of common sense backed, of course, with years of study, hard-gained knowledge, and experience. My first two cases had provided valuable information that had made a difference. Perhaps forensic palynology had a future.

  6.

  ‘I PUT IT TO YOU THAT YOU WERE THERE.’

  I was not the first person to realise that botany could be useful in the world of forensics. Identification of the wood used to construct a home-made ladder was instrumental in securing the conviction of Richard Hauptmann, who kidnapped and murdered the baby son of the famous aviator Charles Lindbergh in 1934. Hauptmann’s trial was one of the first media circuses – one of the first ‘trials of the century’ – and his conviction rested upon the work of Arthur Koehler, a wood anatomist from Wisconsin. By identifying the genus of tree, the milling pattern, and the direction of growth, he was able to prove that the timber used in the ladder, which the kidnapper used to steal into the baby’s room, was taken from the attic at Hauptmann’s own house. Hauptmann was strapped into an electric chair in April 1936, paying with his life for his crime, and all down to the testimony left behind by a piece of wood.

  Nor was I the first person to identify pollen grains in the quest to solve a case of murder or missing people. The first record we have of a police investigation using palynomorphs goes all the way back to Austria in 1959, and the disappearance of a man sailing down the River Danube. Without a body, police had little to work with until the investigation turned to Wilhelm Klaus, a respected palynologist from the University of Vienna. Klaus was given the boots of the missing man’s close friend and, by microscopic analysis, was able to identify an assemblage of modern, well-preserved pollen of spruce, willow, and alder trees. But there were also fossilised grains of hickory pollen. The distribution of these deposits was specific; they were peculiar to a small area located 12 miles north of Vienna. Klaus told the police where to look and the suspect was so shocked at the evidence that he confessed and led investigators to the body. Klaus had envisaged that place using his knowledge of botany and geology of the region.

  These people, among others, went before me with their forays into forensic ecology but, in Britain, the potential of botany to contribute to criminal investigations was hardly exploited before the Hertfordshire case, and most countries of the world are still unaware of what has been achieved. My challenge, across the years, has been to bring a range of specialisms together to form the basic tenets of forensic ecology, and to share this knowledge as comprehensively as I can.

  Palynology was already a well-established discipline by the time I made these first tentative steps, but transporting an academic discipline into the world of police work presented a succession of unique challenges. The truth is, those challenges have not stopped to this day, and they never will. The range of variables in any environment is so wide that each new murder, each new missing person, vicious assault, or rape presents a unique set of circumstances. A discipline like ours advances by degrees – it is cumulative. The natural world is a complex set of different interacting systems, and to perform at their best, a forensic ecologist must have good ecological training and understand the interaction between organisms and their environment, both physical and biological. They usually have one or two areas of considerable expertise, for example, botany, palynology, and soil science, but also some knowledge, and certainly an appreciation of entomology, bacteriology, mycology, parasitology, and zoology, as well as chemistry and statistics.

  By trial and error, I have spent the last quarter of a century developing the protocols by which the discipline is now defined, but the simple truth is that no two situations are the same, and there are very few fixed rules and protocols that can apply to them all. Often, I have been ‘flying by the seat of my pants’, having to invent ways of retrieving palynomorphs from various objects and materials while at crime scenes, or in the mortuary. Eventually, from sheer, grinding experience, I was able to publish a list of protocols for forensic palynology. These contain nothing fanciful, but my findings have, on many occasions, demonstrated that accepted wisdoms in classic palynology have had to be jettisoned to cope with reality.

  The plant kingdom is vaster than most of us can imagine. Excluding algae and mosses and their allies, it is estimated that there are about 400,000 species of plant, with about 370,000 producing flowers and pollen. The rest produce spores. New species are being discovered regularly and, in 2015, over 2,000 new species were identified. When it comes to fungi, we are in a different ball game altogether, and estimates of species are in the millions. Every year, the number that is new to science is huge, and it seems that the count is limited only by the availability of competent mycologists – those who study fungi. Even in my own forensic cases we have identified several new species.

  We will never know how many animals, plants, fungi, and other organisms there are on this planet. And it is chastening to think that most that ever evolved and lived have now become extinct. The vastness of the biological world today is a small remnant of what Earth supported in the past, and no single lifetime would be enough to acquire the skill needed for identifying even a small part. But, being able to identify accurately organisms, or parts of them, is important to a good biologist, and absolutely essential for forensic work. Accurate identification of families, genera, and species can represent the difference between life-imprisonment or freedom for someone.

  The specks and fragments of the environment which get picked up when you contact it, whether it is on your clothing, footwear, hair, garden spade, or vehicle, are proxy indicators of that environment. They are the trace evidence that may link you to a certain place at a certain time. It could be a whole stand of vegetation; it might be an entire plant, or part of a plant; it might be roots, wood, bark, twigs, leaves, stem, flowers, or fruit; more likely, it is smaller still – pollen from conifers or flowering plants, or spores of mosses, ferns, and fungi. The tiny, invisible proxy indicators like pollen and spores are particularly valuable because they are invisible to the eye, so you cannot see them to remove them. You are unaware of their presence, and it would be hard to get rid of them even if you were. They can be a clandestine record of where you have been, and what you have been doing.

  Fungi are particularly interesting because they can act as secondary proxy indicators. They may be growing on a plant; you may not pick up the pol
len of that plant, but you might find the spores of its fungal parasite which may always be associated with it, as in the case of the primrose mentioned earlier. In principle, by finding an assemblage of palynomorphs on a suspect or victim’s clothing or, in other cases, the car in which they travelled, the tools they used, or even the insides of their bodies themselves – we can conjure up an image of the kind of landscapes through which they have travelled or what happened to them. If this sounds simple at first, a case of joining the dots and marrying one imagined landscape to another, the truth is anything but. In reality, the detritus we salvage from a person’s clothing is a chaos of different microscopic particles, many of which will be unidentifiable and unhelpful in terms of constructing our landscape.

  The outside of the car in my first case in Hertfordshire showed the many and varied landscapes through which the car had travelled in the past months, and the same can be true of shoes, jackets, coats, and jeans which have not been regularly changed or laundered. Finding and imagining the right landscape, filtering the useful data from those that might lead into blind alleys or dead ends, involves nuances it has taken me decades to understand. It demands knowing not only one set of palynomorphs from another – when the differences can already be infinitesimally small – but also the ways in which palynomorph assemblages can lure you into thinking the wrong thing. It is vital to know the way pollen and spores are dispersed from their parent plants and fungi, flowering times, the kind of soils and conditions they proliferate in best, and the kinds of plants and fungi that tend to grow well in concert with one another, benefiting from the same kind of conditions.

  Plants that thrive in similar conditions will be found in the same habitats. They can form recognisable communities and from them we can extrapolate a great deal. If somebody gave me an assemblage of palynomorphs like bulrushes, reeds, sedges, gypsywort, and purple loosestrife, I might recognise a pond, lake edge or ditch. The species of bulrush might even give information on the degree of flow in the water. Oak, hazel, ash, bluebell, and wood anemone might evoke images of our wonderful bluebell woods which are so peculiarly characteristic of the British landscape. The point is, plants do not grow just anywhere. Everyone knows that you cannot expect banana trees to grow in the wild in Norway, any more than you would expect to find cacti in the Arctic Circle, or polar bears in the jungle. These have their specific requirements and they would not thrive out of them naturally. And yet this is one of the common mistakes made by barristers I have come up against in court. They know little of plant science or ecology, and I have been challenged with ‘dandelions are found everywhere, aren’t they?’ Well, of course they are not and, in fact, finding their pollen gives us quite specific information.