This happens quite a lot. Either it’s saved or it goes in the bin. Rather a gun-to-the-temple situation! Luckily, my volunteers had quite a lot of fun mounting the material and were quite titillated when it came to the cannabis. I am fairly frequently called on to identify cannabis (Cannabis sativa). In one case the owners of a cannabis factory had attempted to destroy the plants by burning them. I’m not sure under what circumstances this happened as often I do not receive the details of the case from the police. The courier delivered a plastic container which contained the shrivelled and partially burnt remnants of foliage. They were heavily damaged and rolled up into a loose ball because of the heat. Straight away it was clear the leaves were cannabis, but I decided I needed to be sure, both for my own personal satisfaction and to ensure I’d not made a mistake! I carefully moistened the foliage until it was rehydrated and more flexible. After about an hour of careful teasing out and coaxing, I had three or four partially intact leaves. I then gently pressed and dried the leaves for a couple of days so at that they would retain their new position and were photographable. In most cases I would compare the leaf material with reference material from a collection but cannabis foliage is so distinctive it’s not really necessary!
As an aside, current government regulations require museums to have licences to hold restricted substances. In itself, this is fine, but the application of the rules is rather ridiculous. Despite repeatedly telling the Home Office that no one in their right mind would attempt to smoke our dope, they still require the specimens be locked in separate cabinets (they are already in a locked facility) and each year the material must be weighed to see that no one has made off with some of it. Why would anyone bother to smoke it? After all, the specimens are glued to the paper. Either you’d have to role a joint with a whole herbarium sheet or scrape off the leaves from the paper. On top of that, most of the NHM plant specimens, like other museum collections, are contaminated with naphthalene or mercuric chloride and are over a hundred years old. There’s not much tetrahydrocannabinol left.
The FSS herbarium is now safely ensconced in the British and Irish Herbarium of the Natural History Museum. In 2010, shortly after the collection was rescued, the government announced that it was closing the FSS. It was making a financial loss of about £2 million a month. By coincidence, one of the people I knew from ‘down the pub’ was a senior member of staff at the FSS. It was his dream job, or so he thought, until he was told to make everyone redundant, including himself. My friend endeavoured to prepare the staff for their redundancy and help them secure their futures and their careers. Some went abroad, some started working in the private sector and others left the profession. At the same time, the FSS had to repatriate millions of exhibits to police forces across the country. As you can imagine, the forces were not given any additional help to accommodate this influx.
Overall, forensics in this country is not in a good way. The private sector rapidly expanded following the closure of the FSS in 2010. The private companies often have specific skills or areas of expertise that they promote. Some are largely focused on human DNA work. Other companies specialise in trace evidence such as fibres or gun-shot residue. Some of the larger companies have a wider scope and take in the identification of bones, geographic information systems (GIS), archaeology and environmental forensics. In many cases, these are skills that were once found within the FSS or some police forces. More recently, parts of the private sector appear to be contracting and facing severe challenges, mainly owing to the very significant cuts that have affected police budgets over the last decade. Early in 2019, the House of Lords Science and Technology Committee completed their inquiry into the state of forensic science in England and Wales. Many of the people going before the committee expressed significant concerns, and some did not feel that the current situation is sustainable. The published report was damning – ‘The evidence we received points to failings in the use of forensic science in the criminal justice system and these can be attributed to an absence of high-level leadership, a lack of funding and an insufficient level of research and development. Throughout this inquiry we heard about the decline in forensic science in England and Wales, especially since the abolition of the Forensic Science Service.’. There is widespread concern about the significant decline in the quality of forensics in England and Wales. Addressing the committee, the President of the International Association of Forensic Sciences, Professor Claude Roux, said ‘When I was a student, England and Wales held, essentially, the international benchmark. It was the ‘Mecca’ for forensic science. Some 30 years later, my observation from the outside … is that it has been an ongoing national crisis and, at this stage, is more of an example not to follow.’. There is also widespread concern within the criminal justice system about the ease with which unscrupulous or foolhardy people can be accepted as expert witnesses. Many feel that there are insufficient mechanisms for ensuring that potential expert witnesses are suitably qualified or experienced and that they understand and observe their duties to the court.
Personally, I feel that the police are less and less willing to try what are, to some of them, novel procedures. Not only do they appear less willing to expend on areas such as forensic botany, they also don’t seem to have the time to learn about what can be achieved. Over the last three years I have offered to visit several forces to provide CSMs and detectives with information on what ‘flowers’ can do for them. Disappointingly, I have not had my offer taken up so far. I don’t think this is hostility to the idea; sadly, I don’t think they have the time. They barely have time to think, let alone plan. I can see it in their eyes. They take my business card, express enthusiasm for the idea of a seminar session and then the encroaching horror of several thousand emails stifles their minds and my card lies forgotten.
Despite the short-term gloom, I do feel that environmental forensics can improve the outcomes of criminal investigations. Forensic botany and some other areas of environmental forensics have yet to fully embrace sequencing is often confused with DNA fingerprinting (also called profiling). Sequencing is identifying the individual building blocks of our DNA, the nucleotides, while fingerprinting aggregates blocks of nucleotide code. Fingerprinting is rather like describing the make-up of a very, very long street by giving house numbers and noting whether each property is modern, Victorian or Georgian. Sequencing is rather like taking each house apart and documenting each block of stonework or brick.
Over the last few years, the technologies used in DNA sequencing have advanced considerably. Not only are we able to retrieve more data, we’re are able to do it more quickly and more cheaply. Importantly, our ability to retrieve DNA from badly degraded or mixed samples has improved vastly. The advances in the retrieval of ancient DNA offer great potential for revisiting ‘cold cases’ and examining exhibits for traces of non-human DNA. Ancient DNA is simply the DNA that remains on old and degraded biological material. The technologies used to retrieve it were largely driven by the desire to extract DNA from extinct organisms and subfossils. For example, in the world of botany these technologies have been used to extract DNA from 300-year-old herbarium specimens to help understand the domestication of sweet potato (Ipomoea batatas). For those of you who are gardeners, you may recognise the name Ipomoea, since it’s the genus to which morning glory belongs. We are now able to extract DNA from the surfaces of walls, shoes, soil or almost anything that has come into contact with biological material.
The discipline which has become known as environmental DNA (eDNA) largely has its roots in the work of conservationists and people aiming to control the spread of invasive species. One of my favourite examples of this work is a project in the Great Lakes region of North America. The Great Lakes are under serious threat: amongst other things, they are being damaged by pollution and invasive species. One introduced fish species, the sea lamprey (Petromyzon marinus), has been causing significant damage to fish stocks in the lakes since the first half of the twentieth century. Control of the sea lampre
y has traditionally been carried out by poisoning with lampricides. Unfortunately, these chemical also harm the non-invasive lamprey species that are found in the lakes, as well as affecting other fish, such as sturgeon, and amphibians. Researchers from the University of Manitoba have recently developed a way of isolating sea lamprey DNA from river or lake water. How is this done? By tracing their wee. All animals must excrete waste, which is removed by urination or defecation. In among those waste products are cells from the animal’s body. The test the scientist developed is not only able to detect sea lampreys, it is also able to tell their DNA apart from that of non-invasive lampreys living in the region. Knowing where the invasive sea lampreys are means that less environmentally impactful control measures, such as sex pheromone traps, can be used to control their population.
Using plant-DNA-based information in criminal investigations has been done. I’m not aware of any cases in the UK, but DNA fingerprinting of plants has been used in the Netherlands and in the US. Plants, like animals, rely on DNA to encode the fundamental chemistry that makes each one of us unique. However, there are exceptions. In the botanical world many plants are clonal, which means they have the same genetic make-up as each other. A typical example is the strawberry: each parent plant produces new plants by growing runners that sprout plantlets at their tips. Each one of these ‘daughter’ plants will be identical to the original plant. A common house-plant, the spider plant (Chlorophytum comosum), does the same thing: each plant has identical plantlets hanging from the ends of their floppy stems. Some naturally occurring clones can be huge; a clone of the quaking aspen (Populus tremuloides) in the Fishlake National Park in Utah, USA, covers 43 hectares (106 acres) and is estimated to weigh over 6,000 tons. This clone, known as ‘Pando’, has been estimated to be 80,000 years old. Clonality also occurs in animals. It is rarer but has been reported in some snakes, sharks and many invertebrates such as aphids.
Genetically identical plants pose a problem for forensic botany. It is unlikely that an expert witness will be able to demonstrate to the court that a suspect was at a crime scene if it is known that identical versions of the plant are found in surrounding locations and further afield. Luckily, many plants are not clonal, and plant-based DNA has been used in the courts. In Arizona, USA, the fruit of the blue palo verde tree (Cercidium floridum) collected from the back of a truck in which a murder victim had been transported, helped link the suspect to the crime scene. Using plant DNA, scientists were able to demonstrate that the fruit originated from a tree in the grounds of a factory where the suspect, Mark Bogan, was believed to have dumped the body of his victim, Denise Johnson. Bogan was subsequently found guilty of the murder. This 1992 case is notable as it was probably the first occasion that plant-DNA-based evidence was used in court. Such evidence remains very rare in criminal courts. The strongest barrier to it being used more widely is financial. Historically, DNA-based work has been very expensive. Thankfully, with new technologies, costs are falling, and I believe it won’t be long before these techniques are more widely available.
The ability to identify a single species from an environmental sample can be turned on its head. Technically, it is now possible to build a comprehensive profile of the organisms present in a sample. It is quite amazing how many organisms are living under our noses in the most apparently inhospitable environments. A few year ago, the Natural History Museum launched a citizen science project called Microverse to investigate the microbial diversity of walls and hard surfaces in the built environment. The results astounded them; the abundance and diversity of microorganisms such as bacteria and fungi were far greater than anticipated. On top of that, the researchers found that they were able to separate microbial communities from different types of habitat. Those living on brick were different from those living on concrete, and the microbial communities found on older walls were not the same as those living on newly built properties. We are now in a position where we may be able to use those findings to identify where a suspect has been and provide robust evidence of that.
So, what’s stopping us? Again, it’s basically money. Before science such as this can be used in the courtroom there needs to be a lot of work. In the first instance, the core techniques need to be refined through a structured research programme. Further work includes developing cost-effective means of applying the science in the forensic environment, training CSMs and detectives, and ensuring that the approach is acceptable within the court system. This may seem like a lot of hard work but, as criminals become more aware of what ‘not to do’, there is a need for new and increasingly sophisticated tools to ensure the guilty are caught.
I’ve often enthused about the fungal organisms of this planet at various points throughout this book, which isn’t surprising, considering my doctorate was on the evolution of some of these fascinating organisms. Appreciating the diverse ways microbes and fungi interact with us after we are dead is key to exploring the application of this knowledge in the forensic environment. One of my favourite groups of fungi are the Onygenales. Onygenalean fungi are particularly good at breaking down keratin, the complex protein that provides substance to the outer layer of the skin as well as hair, horns, claws and hooves. They are very specialised. Some are very familiar, such as the unpleasant athlete’s foot (Trichophyton rubrum) or ringworm (caused by several different species). Some are important causes of human diseases. Others are more esoteric and have very particular requirements. One species, the horn stalkball (Onygena equina), lives on the horns and hooves of sheep, goats and horses. If you are lucky and very observant, you may find horn stalkball growing on the remains of dead animals on a country walk. Understanding how, and how fast, fungi such as the horn stalkball colonise mammalian skin, nails and hair would not only be fascinating, but it could offer important insights for forensics. If we can estimate how long a fungus has been growing, we may be able to estimate how long a person’s remains have been where they were discovered.
At several points during my career in forensics I have been asked to examine fungi growing on the skin of the dead. The first case involved an infant. In fact, this was my very first case, long before I attended the suspected crime scene I described at the start of this book. I was sent pictures and asked whether it would be possible to estimate how long the child had been dead based on the growth of the fungal colonies on their skin. I found this very challenging. The pictures were graphic, the first of this nature that I had encountered. More importantly, very little is known about the types of fungi that colonise our skin after death. It was possible that the fungi might have been one of the organisms causing athlete’s foot or ringworm, or it might have been something else entirely.
I advised the police that I would need a live sample of the fungus, first to identify it and then to find out how to grow it. Culturing fungi can be extremely difficult. Many have very complex and specific nutritional requirements and can be very picky feeders. The trick is to emulate their preferred food source. In this case I was planning to use one of the standard meat broth agar media. Agar media are used by biologists for growing fungi and bacteria. The media is made by cooking a broth of nutrients, such as boiled bones, and agar. On cooling, the broth sets into a firm gel upon which the fungus or bacterium can be grown. The reason the broth sets into a gel is because of the agar, which is extracted from algae, usually Gelidium spp. The meat provides the core nutritional needs of the fungus and the agar provides a physical base on which to grow the fungus. You may find this surprising, but microbiologists often have their own preferred recipes for the cultivating of fungi and bacteria. When I was doing my laboratory work for my PhD on Peronosporomycetes (yes, that word again) I used to grow my fungi on cannabis seed, termite wings or the skin scales of snakes. Cultivating the fungus from the exhibit would be essential, because without a live fungus to experiment on, I would be unable to estimate the growth rate. I was assured that a sample had been collected and would be sent immediately. After two weeks, nothing had arrived, so I contact
ed the police who informed me that they had lost (or damaged) the sample!
Clearly, losing evidence is very poor conduct. But this tale also leads me to another observation. In my experience, there is very little knowledge in some police forces or forensic service providers about how to correctly store living material or preserved biological specimens. On the occasions I have been asked to examine fungal colonies growing on the dead it has been evident that the fungus was stored poorly and was very likely to be dead. This is unfortunate, because it is likely that fungal and bacterial colonisation of skin surfaces may be useful in determining how long someone’s remains have been in a specific environment. Consider this hypothetical situation: a person is killed in a building, and is then stored for several days in that building before being moved to a convenient location in woodland. Being able to provide separate estimates of the post-mortem interval and the duration of that person’s remains having been in that woodland could be vital in understanding how the crime was committed.
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