We asked the police if we could use facilities at their forensic laboratory and, although they did not have anywhere dedicated to microbiology, they did have a good laminar flow cabinet which would protect my preparations from stray spores in the air. As usual, we had all our small pieces of equipment with us, and I set up a makeshift inoculation facility in the cabinet. All I needed was a Bunsen burner for sterilising and Petri dishes with some basic medium. I carefully made cultures of a number of colonies onto plates of medium.
For a long time, David had been the Director of the International Mycological Institute at Kew and, for most of his working life, he had had technicians to carry out the drudgery of the technical work – sampling, sub-sampling, culturing. I, on the other hand, had never had the luxury of a minion to carry out work on my behalf, so I have always retained my practical skills as a microbiologist – and, after photographing and drawing the patterns of fungal growth on the various fabrics, I defined representative areas for sampling, and measured all the most clearly defined colonies that were in my drawings. I then cut out the samples of fabric, cultured each colony onto agar plates, and put the samples into sterile containers. We then flew back south with our mouldy bits of carpet, cushion, and precious cultures, and set about an experiment to understand what the fungal growths represented in that apartment.
Our first step was to incubate the mouldy fabrics at the same temperature as in the flat. When, four days later, the fungal colonies looked exactly the same as they did when we originally cut them out of the cushion and carpet, it was obvious that their growth had been halted by something, and that something was probably a lack of available water.
To test this point, we wetted all the fabrics with bovine blood and incubated them overnight. By the following morning, fungal growth had been explosive. Each fungal colony had spread out, fighting for space, overgrowing each other wherever they could, and there were no gaps at all. Now we had a working theory. The warmth of the flat had dried out the body fluids and, as soon as it became dry, the fungi just could not spread any further. By measuring the size of colonies growing on the carpets we could establish the minimum amount of time the body had lain there if we knew the rates of growth of the various fungi.
This meant taking each pure culture, prepared in Dundee, and sub-culturing it in the middle of a new Petri dish of growth medium. The fungus would then grow outwards from the inoculum to form a circle. We then watched, measured, and timed the spread of the three isolates, which David had identified as Mucor plumbeus, Penicillium brevicompactum and Penicillium citrinum. The incubator was set at 26°C and, after two days, the Mucor, being a fungal ‘weed’, had virtually covered the whole plate as we expected. It took five days for the two Penicillium species to reach the same diameter as they had reached at the crime scene. This meant that the blood had been spattered on the cushion, and seeped onto the carpet, a minimum of five days before the body was found. What really amazed us was that the offender, a ‘friend’ of the victim, later admitted the crime and confessed that it had been committed five days before the alarm was raised. If the windows had been left open, flies might have got in and, inevitably, the police would have asked an entomologist to estimate the time of death. Yet again, we had shown our usefulness when the tried and tested methods just do not work.
Fungi can also provide excellent primary trace evidence, or even provide corroborative support to botanical or palynological evidence. They are useful because they can grow wherever there is even a tiny splash of food – on glass, paper, wood, leather, and even plastic. Fungi have adopted many different kinds of lifestyle. They may simply feed on dead organic matter, and this is why the leaves in an orchard disappear by the spring, or they may invade and parasitise a host, even killing it so that they can feed on the dead body.
Some fungi form intimate and mutually beneficial relationships with plants. The plant feeds them sugar and the fungus gives the plant phosphate, water, and other nutrients. As the fungal mycelium spreads out into the soil, it effectively extends the root system of the plant. I find it even more wonderful that one such fungus can form the same relationship with several plants at the same time, and food can pass throughout the system. This means that plants can be linked, and one that is struggling might be fed by another plant via the fungus. Thus if a tree is doing very well at the edge of a woodland and one is growing poorly inside, the outer one can pass food to the starving one. When you think that each plant can form relationships with many species of such mutualistic fungi, we can think of vegetation as being all linked up rather than behaving like single individuals. Today, ecologists increasingly talk of the ‘wood-wide web’. The world is so complicated and so incredibly wonderful!
Not all fungi are benign, though, and many are desperate killers. They do not live in harmony with their hosts but invade, kill, feed, and move on, either by spores flying into the air and landing on leaves and stems, or by creeping through the soil to attack roots. Animals also benefit and suffer from fungal infections. Those that live in the animal’s gut actively digest indigestible foods down to simple molecules that can be used by the host. Cows, sheep, and goats chew the cud to make indigestible food like grass, hay, and leaves more accessible to the huge volume of microorganisms in their guts. They would starve without them. The wild rabbit even has to eat its own faeces because the place in its gut where microbes do the digesting comes after the place where absorption occurs. What a freak of nature that is.
Another startlingly robust symbiosis of fungi and plants – and, sometimes, a fungus, plant, and various species of bacteria – is the lichen. Lichens are the scurfy, leafy, or even bushy growths, invariably in shades of grey, green, and black, found on rocks, buildings, walls, tree trunks, leaves, and even on the ground. One looks just like trodden-in chewing gum and, where it grows, a pavement can look really polluted. The lichen partnerships are incredibly ancient and go back hundreds of millions of years. They are exquisitely balanced associations and they can tolerate the extremes of physical and chemical conditions on this planet. They are found in Antarctica and arid deserts but are most diverse in hot, steamy jungles, and temperate forests.
Lichens are the ultimate survivors and have survived space rockets that have crashed to the ground in flames, and a specimen of Xanthoria attached to the outside of the International Space Station for 18 months survived cosmic and ultraviolet radiation, and the vacuum of space itself.
Lichens are ancient and durable, and each one is certainly not an individual organism (any more than you are); it is a microcosmic community of a fungus, one or more algae, and bacteria. Like other fungi, they can be used to give a good idea of how much time has elapsed. Even geologists trying to estimate the growth and decline of glaciers have used them to estimate changes through time. And so it was when, a few years ago, David and I were at a biodeterioration conference in Manchester when the call came through that we were wanted urgently. On a quiet stretch of road, bordered by woodland and 190 miles away, a lorry driver – stopping on the side of the road to relieve himself – had discovered a suspicious bag that he thought might have been a dismembered body part. A murder case, in which the victim had been dismembered, was dominating the news at the time and the public had been asked to look out for anything suspicious.
We were told a bare outline of the case. A man and woman envied the financial status of an associate and decided to kill him. They took over ownership of his house and car, and their naivety in thinking that they might get away with this is overwhelming. The hapless victim had been expertly butchered and his body parts distributed over a wide area. His skull was found in Leicestershire, his torso was found in a suitcase in a Hertfordshire stream, and the arms and legs were variously found on verges, woodlands, and fields. I had worked on several of the discovered body parts, including the skull, but the power of botany and mycology for one leg made an impression on many.
David and I left the conference in a hurry and drove, as fast as speed limits would allow
, down through the Midlands, past Birmingham and all its traffic congestion, to the place where the leg had been found. Cordons had already been set up and, by the time we arrived, the crime scene investigators had already removed the leg to a mortuary; we missed it by 20 minutes. To this day I will never understand why and, pretty fed up at this, and with so little we could do in the fading evening light, David and I decamped to a local bed and breakfast, utterly exhausted after the conference and long drive. The next morning, bright and sharp, we arrived at the site where the leg had been deposited. I started by doing a vegetation survey, assessing possible offender pathways, and taking soil samples for possible comparison with the footwear and clothing of one or more offenders whenever they might be apprehended. When the lorry driver had found the leg, it had been wrapped in blue plastic. He claimed not to have touched anything, saying that he just telephoned the police as soon as he realised there was something suspicious – but, when I looked at the ground, it was obvious that he had had a good poke around the parcel and had certainly moved it about a metre from its original position. How did I know? Well, the original position of the leg was quite clear to me; rodents had nibbled at the blue plastic and earthworms had already started to bury it in their casts.
There were several small herbaceous plants which had obviously been bent over by a weight, but they were still green and had started their recovery growth. The chewed-up bits of plastic and the little herbs were about a metre away from the putative position of the parcel; crime scene investigators had carefully marked the spot they had found it. I already knew that the lorry driver had bent the truth slightly and that his curiosity had resulted in displacement of the parcel. I was doubtful that it had been there for more than a few days because of the state of the plants, and burial of the comminuted plastic was fairly minimal compared to some I had witnessed in other cases. The police investigation was getting grislier by the day. This was not the only body part turning up in a remote location, and David and I had already been to a site to examine the head in Leicestershire, and an arm and another leg at different locations in Hertfordshire. The police already had their suspects and, after interview, had come to the conclusion that the murder had been committed two weeks before the last leg had been found. The assumption was, therefore, that all the body parts had been dumped at the same time, about two weeks previously.
I was kneeling down, looking carefully at the plants that had been affected by the bag, when David poked me in the back and pointed to a twig that was lying on the stem of one of the plants at the original site of the bag. Following his finger, I saw some extensive colonies of Xanthoria parietina on the twig. This lichen is bright yellow with orange spore-producing bodies when in full light – but grey and orange when in the shade, as on the underside of a branch. It is incredibly common in the south of England, especially near to roads, where its growth is stimulated by nitrogen pollution from vehicles. But that was not what interested us here. The colonies on the twigs were indeed yellow, and David knew from field observations that they became greenish if covered, although he did not know how long that took. We felt this might be important, but in that moment we had little idea how useful it would become. We took the twig from the ground, and also some others on nearby branches, and the attendant police officer logged them out of the scene.
There was nothing more we could do until we brought the twigs home to our garden. We live next to one of the biggest oak trees in Surrey, and its leaves are a nuisance towards the end of each year, but now they were useful. We allow the garden to run wild in our little orchard so that the foxes and badgers have somewhere to sun themselves, or to roll and play, as we have seen them do many times. It is also useful for setting up simple experiments to test ideas, and we decided to do this here. David knew that, when in full sun, the lichen was yellow and orange shades but, when covered, for example, on a branch that been turned over, it turned green and eventually died. By determining the speed at which this particular lichen might turn green when deprived of sunlight, might help us to work out how long the dismembered leg had lain in the woodland?
We set up a little cage from chicken wire to prevent any accidental disturbance, and put a thick layer of dead oak leaves on the ground to simulate the leaf-strewn woodland floor where the leg had been dumped. Next, we took three pieces of twig, each bearing a good sample of the lichen, and placed them onto the leaves. The first twig we left completely exposed to the light, while covering the second and third twigs with blue plastic bags full of sand to simulate the weight of the dismembered leg.
Then there was nothing left to do but wait. After two days, we removed the bag of sand from the second twig, but left it in place on the third until five full days had elapsed. The results were interesting. The first lichen, which had been consistently exposed to the light, stayed yellow – and, in fact, slightly yellower than before. It had been given more light than it had at the crime scene and had responded accordingly. The second lichen was yellowish with a greenish tinge, but the third twig, having been deprived of light for five days, was completely green. The ramifications for our case were clear. If this particular lichen turned green after five days of being covered up, and it was still mainly yellow at the deposition site, it meant that the leg could not have been placed over it for longer than five days.
When David and I reported our findings, the police could hardly believe what they were hearing; they had been convinced that the leg had been there for two weeks. The tighter time frame might have upended the accepted wisdom about the case but, as with lots of things in nature, the lichen was not lying. The investigation was not as neat and tidy as the police had supposed.
David and I continued to help with the investigation, now nicknamed ‘the jigsaw case’, of the dismembered man. Eventually, the torso was found. It had been wrapped in a blue towel, put in a cheap suitcase, and dumped in a stream, miles from the limbs we had already examined. We waded in the freezing stream while the torso was recovered, but the best place for examination was the mortuary. This was only the third dead body David had ever encountered in his forensic experience, and his first time in a mortuary. I look back on that day with some regret because I was so insensitive. David is like me in so many other ways that I had assumed he would not be affected by the atmosphere and activities in a mortuary. But I can still see the pallor of his face, and his slight stutter, when I asked him if he would rather measure the fungal colonies on the torso or kill the maggots in hot water in preparation for the forensic entomologist. He opted for the maggots and I remember him being incredibly quiet in his little corner of the stainless steel bench with his kettle and bottles. Later, he confessed that he hated killing those wriggling little things, and especially killing the pretty beetle that had unfortunately joined the feeding throng inside the suitcase.
What began with a leg discovered on the edge of a roadside ended with the revelation of a story so vile that the most imaginative crime novelist might have struggled to make it up. After being invited to become a lodger at his friend’s home, and growing envious of his new landlord’s financial status, the killer and his girlfriend, a much younger prostitute, and the mother of two girls, conspired to kill him. Stabbing him in his back as he slept, the lodger, who had been a butcher in a previous life, and was reputed to dismember bodies for criminal gangs outside London, took to his old trade, carving up his former friend and scattering him far and wide. Perhaps they thought they would never be caught – but, as I have seen time and time again, the tiniest hint from nature can help point us in the right direction so that justice can be served.
10.
LAST BREATHS
Our bodies are dynamic and constantly changing. This is because they are being built up and broken down by our own biological processes all the time. As we breathe the air, and eat our food, we are taking the outside world into our own ‘inner sanctum’ and, put simply, we take what we need and eject anything that is unwanted in the form of sweat, urine, and faeces. What most p
eople cannot realise is that there are tiny amounts of radioactivity in our food and water, and these get built into our soft tissues, bones, hair, and nails. Every part of the world has its own radioactive signature in the form of radioisotopes and, because of these signatures, we are able to trace your geographical movements since you were born. A tooth will identify your place of birth, a femur will tell us about your travels within about the last ten years because the bone is turned over every decade, and your hair and nails give information about where in the world you have visited more recently. It takes about one month for one sixth of your fingernail, one twelfth of your toenail, and about 1.3cm of hair next to your scalp to grow. This means that information of your whereabouts, month by month, can be tracked.
The air provides the oxygen we need to release energy from our food but, as we breathe in and out, our bodies can retain traces of the geographical location you breathed in the air. As well as radioisotopes, the air is full of particles and debris and, if you are ever in any doubt about this, spare a thought for all those whose eyes start streaming, and noses start running, on a dry summer’s day. Anyone who suffers from hay fever will attest to the fact that the air we breathe is full of pollen grains, plant and fungal spores, as well as other, unknown, allergens.
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