Murder Most Florid

by Mark A. Spencer

  The clothing and personal possessions of the dead are some of the most challenging exhibits. Very often they are degraded by the weather or decay, and they may be very smelly. Sometimes, I find the patterning of the stains quite hypnotic; each stain is a trace of what happened to the person. One of the more awful exhibits I had to examine was a partially destroyed suitcase. The suspect, who was subsequently found guilty of murder, had killed his victim and then placed the body in a suitcase. After disposing of the body, the perpetrator attempted to dispose of the suitcase by taking it to another location and partially destroying it by cutting it to pieces and smashing up the frame. Somehow the broken-up suitcase felt like an echo of the brutality of the murder. The attempt to destroy the suitcase may have been emphatic but it was also ineffectual; on the outer surface of the suitcase there was soil trace evidence that helped find the man guilty.

  It is strange how we are affected by fragments. A novel may contain a scene that details a person in pain holding a broken and fractured relict of something or someone lost. Sometimes I find myself more affected by a pottery sherd recovered from a Bronze Age hearth in a museum than the fully restored artefact, even if the intact object is a thing of great beauty. Perhaps it is the niggling horror of the missing. For some reason, every time I see the Rosetta Stone, I feel a gnawing sensation caused by the missing parts. It drives me slightly potty – surely ‘they’ can find the rest.

  Vegetation fragments can be very powerful tools in understanding how a crime happened, and I often receive leaf fragments from a crime scene. They are usually tiny and very badly damaged by abrasion, by the weather or the processes of decay. Each one may help tell the story of what happened, and every fragment is emblematic of a life lost or shattered.

  Several years ago, I received two tiny pieces of leaf that were recovered from a victim of a violent sexual assault. After the crime, the traumatised person fled the scene, but they were unable to recall where the attack had happened. The police were hoping these fragments could be used to localise where the crime had occurred. For me, these leaf fragments shuddered with potency, they were witness to the awful event that had engulfed the victim. I carried them around the laboratory with great care, not just because of the need to treat the evidence professionally but because they had ‘experienced’ something awful. Through these tiny pieces of battered greenish-brown tissue I was connected to someone I would never know.

  Botanists usually identify plants from whole specimens or a selective gathering that enables us to work out what the plant is. Most botanists rarely work with a torn piece of leaf that is less than a centimetre across. I tell you, it can be very difficult. The main reason is that there are a huge number of wild plants on the planet. The most recent estimates are around 320,000 species, which is a lot to remember (and realistically it cannot be done - even the best botanist has probably only got good recall of a few thousand). Obviously, not all of these grow in the wild here. The majority are tropical, but here in Britain and Ireland there are about 4,800 species of native and non-native plant growing wild.

  Most of that number are of very limited occurrence or found at significant distances from the crime scene I was investigating, which left me with only a few hundred to contemplate. The reticulate patterning (think of a street map of medieval London) of the leaf veins allowed me to conclude that plant was not grass- or lily-like, as those plants have parallel veins (like the multitude of railway tracks running into Clapham Junction). This observation knocked out many other contenders. My mind started flailing around, hunting for solutions. Sometimes, this the best way to start; I don’t know of any online resources or one-stop textbooks that deal with leaf fragments. I spent an hour or two pulling ideas out from the recesses of the botanical parts of my brain, forty odd years of detailed study, random observations and fleeting memories. In the back of my mind I had a strong feeling that the leaf fragments came from a tree or shrub. Needing to gain a little control and structure to my mental meanderings, I decided it was time to be a little more systematic and reached for the standard text for field botanists in Britain and Ireland, Clive Stace’s third edition of the New Flora of the British Isles (this work has now been superseded by a 4th edition). It’s quite chunky and has a reputation for terrifying the less experienced. My nickname for it is ‘Regal Stace’, partly owing to the purple colour theme of its cover and because of its august position in botany! I turned to the index at the back with the aim of jogging my memory by scanning through the alphabetic list of plant names: Abies, Acanthaceae, Acanthus, Acer … I stopped at Betula, feeling a tingle of connection. Perhaps it’s one of those? That would be very handy – it was a long way to Zosteraceae.

  I paused and considered what to do next. I instinctively felt that I had the answer, but that was not enough. I would need to make sure my tentative observation withstood scrutiny in court. The best way to do this is by verifying my identification. It is possible to use online resources, as there are huge quantities of photographs of plants on the internet. Unfortunately, many are of poor quality and incorrectly labelled. Also, in most cases they are not scientifically validated. Submitting a report with a statement saying I’d compared evidence from a serious criminal investigation with images from Wikipedia is unlikely to be well received by the court, although the opposing barrister may be delighted. It is wiser to use real plant specimens from an herbarium; these have the advantage that I can compare the exhibit with the herbarium specimen under a microscope. Herbarium specimens are (or should be) identified by experienced botanists. Each specimen will have a ‘determination’ on them – this means that a botanist has validated the identification. I headed into the collection store and found material of British birches and started to make my comparisons. The leaf fragments were a match for one of our native birch trees, the silver birch (Betula pendula).

  I contacted the forensics company I was working with and we arranged a scene visit with the police. As usual, when we got there, it was freezing. The search area encompassed several hundred yards of roadside verge and tracks. It was quite a bleak and isolated place on the outskirts of a small town in southern England. The most abundant trees and shrubs were hawthorns, oaks and ash. After a careful walk back and forth, I found two small areas where silver birch grew. Despite it being early winter, the fallen leaves had not been blown around in the landscape. I informed the detectives that I was reasonably confident that the sexual assault had taken place at one of these two locations.

  As is so often the case, I didn’t hear from the police about how the investigation proceeded.

  In some cases, I am a fleeting presence in the work of the investigating team. I suspect that if the police were less busy, they would be inclined to let specialists such as myself know the outcome of an investigation. I think it simply slips their mind, since, often as not, each investigative team will be working on several cases at a time. I would very much like to hear from the police, learning from them what worked and what didn’t would be very helpful. But I can’t pick up the phone and badger them!

  While they might not appear so, leaves are remarkably complex structures. Each leaf or, more often in crime-scene work, leaf fragment, can tell an experienced observer a lot about the origins of a plant. The main function of a leaf is to increase the surface area of a plant, which is important for two vital functions, respiration and photosynthesis. The size and form of the leaf is constrained by the environmental conditions that the plant evolved in. Predation is also a factor as leaves are often tasty! These evolutionary pressures make leaves highly diverse.

  One of the more variable features of leaves are their hairs. Some plants have none, others are very hairy. The main causes for the development of hairs in plants are predation, water loss and sunlight. Obviously, predators come in all sizes and shapes. Larger grazing animals are usually deterred from eating a plant by toxicity or pain. The common stinging nettle (Urtica dioica) is a well-known example of this. The hairs of the plant have brittle, sharp tips
that readily break off, penetrate the skin and inject formic acid, histamine and acetylcholine. As much as we grumble about the painfulness of these stings, other plants can pack a much stronger punch. Most famously, the stinging nettle’s larger, scarier cousin, the gympie-gympie (Dendrocnide moroides), from Australia, has been known to kill horses and dogs; the pain is excruciating and lasts for days. The impact of feeding by smaller animals is reduced by having hairs as a barrier to movement. Imagine you’re an aphid: you’re less than a millimetre high and you need to clamber through hairs two or three times your height – it’s tough going, a bit like walking through a bamboo thicket. Incidentally, by slowing you down, the hairs also make you far more vulnerable to predators such as ladybirds.

  Many plants grow in arid habitats and being hairy can help reduce water loss by slowing the flow of air over the surface of the leaf and increasing humidity. And, even though they are often very small, each hair casts a tiny shadow, which reduces the amount of sunlight hitting the leaf surface and lowers the temperature of the leaf. At higher altitudes or in very sunny environments the hairs also protect the leaf from damage by ultraviolet radiation. When I see a plant with very hairy grey leaves, I know that it is very likely to come from a hot, sunny, dry environment, somewhere like the Mediterranean. These visual cues are also of use to gardeners − most grey-haired plants rarely do well in shade, so give them lots of sunshine. Most of Great Britain and Ireland is not very dry, therefore relatively few of our wild plants are densely haired or grey-coloured – those we do have are largely confined to coastal areas in the south-eastern parts of these islands. Nevertheless, many of our plants do have hairs and they can be very varied in form. This variation can be key to identifying a leaf fragment.

  Leaf hairs are made of plant cells. Sometimes a hair can be a single, long, thin cell or it may consist of several cells making a chain, rather like the carriages of a train. Some of these hairs are very short, less than a fraction of a millimetre long, sometimes they can be several millimetres long. Even within these so called ‘simple’ hairs there is further variation. Some may have enlarged bulbous bases; others have globular, glandular cells at their tip that may contain volatile oils. These glandular hairs are typically very common in members of the mint family (Lamiaceae), one of the larger plant families in the world, with about 7,500 species. In Britain and Ireland, there are about 80 wild species and hundreds of cultivated varieties in gardens. The aromatic, volatile oils found at the end of glandular hairs are what give members of the mint family, such as thyme, rosemary, basil and sage, their distinctive smell and taste. They also ward off certain grazing animals and reduce water loss.

  Perhaps the most distinctive hairs found on plants in these islands are those that branch. Branched hairs can be very diverse in form. Some members of the daisy family (Asteraceae) have branched hairs that divide in two and look rather like tiny tuning forks. To the uninitiated, some of these plants with tuning-fork hairs look very similar to dandelions (Taraxacum). Among other features, leaf hairs are what botanists use to distinguish the tuning-fork-hair-bearing hawkbits (Leontodon) from dandelions. Hawkbits are examples of fairly common and widespread plants that have rather specific habitat requirements. They are unable to cope with grassland that is too dense or full of nutrients. You are unlikely to find them on new lawns or football pitches, but you are likely to see them growing on dryish, free-draining soils with a wide range of other plant species. Finding the hairs of hawkbit in a sample would certainly help me localise the kind of environment the sample came from. Sadly, dandelions are not so helpful. As things stand, we know of nearly 250 species of dandelion in Britain and Ireland. Many of these are widespread and common, while others are very rare and restricted to specialised habitats such as mountain tops or ancient fens. The trouble is, they are rather hard to identify at the best of times. Undamaged mature leaves, flowers, pollen and seed need to be examined; they are almost impossible to identify from a leaf fragment. So far, I have not thought of a way in which I can use dandelions in forensic casework.

  Some of the most beautiful hairs are also some of the most distinctive. Many of our wild plants have variations on a star-shaped pattern; these branched stellate hairs often look like thin-limbed octopuses or starfish. They also have the advantage that they tend to break off easily and can become attached to clothing, carpet or hair, and so have the potential to be very useful in forensic work. Some members of the cabbage (Brassicaceae) and mallow (Malvaceae) families have very distinctive stellate hairs, as do ivy and the invasive non-native buddleia.

  Presenting scientific information is not always easy. I need to be able to present my observations verbally in a way that aids an active investigation. Dazzling a CSM with my knowledge of Peronosporomycetes (my PhD subject) is not going to help. Retaining scientific rigour whilst being accessible to the non-expert can be challenging. Writing reports, both for the police and for the courts is a slow and, at times, tedious job. Each word needs to be carefully considered and every piece of information carefully checked. The slightest mistake is just what barristers are looking for to demolish you in court. A thoughtfully worded report is an important step in ensuring that all my observations and actions are clearly presented. It is also important that the information and reasoning behind my conclusions are evident. Apparently minor errors in referencing of information such as dates, times or exhibit numbers are potentially catastrophic − they are just the sort of lapse that a barrister needs to cast doubt on the credibility of an expert witness. A poorly written report is very likely to result in a court appearance that will be a very unpleasant experience. Having said that, a scientifically robust and well written report does not guarantee an expert will be spared a grilling. If there is something that is contentious or needs examining, the expert witness will be called. To date, I’ve submitted quite a few reports, but I have only been called to court three times.

  Waiting to be called to give evidence can be both tedious and anxiety-inducing. My mind races through the report, hunting for errors and panicking when I think I have found some. I have an encrypted hard drive that I keep my forensic casework on, and this will come out so that I can read past emails and check images for overlooked information. Luckily, we’re rarely alone as expert witnesses. There will usually be several of us, each undertaking our own tension-management regimes. We all end up with the demeanours of teenagers cramming for an exam; some of us flashing our confidence, others taming their fears. At the last court case I attended, there were five of us waiting to give evidence, each with our own specialisms. Alongside me was a biological statistician, a gunshot residue expert, someone who analysed shatter fragments patterns in glass, and another who worked on DNA. That’s a lot of scientific information for a jury to understand in one day.

  Even though an expert witness may be engaged by either the prosecution or the defence, the primary duty of expert witnesses is to the court. In other words, we must aim to present our evidence and conclusions in an unbiased manner. I and other expert witnesses are required to comply with what are called The Criminal Procedures Rules. These rules govern what the duties of an expert witness are and how to conduct our work. I have also undergone extensive background and security checks; these are reviewed on a regular basis to ensure that I am still of good character! This fact usually results in mirth from my family and friends who invariably think that my character is certainly open to question.

  Archives and data sources are essential when doing any form of research, and this is certainly true when examining evidence. I would dearly love to have a digital photographic archive of the fruits and hairs of plants found growing in the wild and in our gardens. It would be very handy and save a lot of time. Unfortunately, no digital archive currently exists in the United Kingdom and is unlikely to in the current economic climate. In the meantime, I continue to verify my plant fragment identities the traditional way, using an herbarium.

  Herbariums are the single most valuable resource for my work.
My quick and dirty explanation for them is that they are essentially plant libraries. But that does not fully do justice to them. Libraries are wondrous places but, in the main, they contain copies of material that can be found elsewhere. Each item in an herbarium, however, is unique. An herbarium is a collection of pressed, dried plants. In previous centuries they were mounted in bound volumes and called hortus siccus, which means ‘dried garden’. Today, each specimen is mounted on an individual sheet. Each sheet has information on where, when and by whom it was collected, as well as the plant’s scientific name. Hopefully, it will also have a unique identification number; the reason herbarium sheets have these is that there are about 350 million specimens in the world’s herbariums. It’s incredibly easy to mislay a sheet, and having a unique number helps curators keep track, especially as many institutes loan them to other organisations for research purposes.