A little over 10 years ago, Dr Mark Spencer received a phone call from a crime scene investigator asking him to assist with a potential murder enquiry.
The heavily decayed remains of a man had been found. The remains were surrounded by vegetation, and the investigator wanted to know if Dr Spencer would help identify how long the body had been there.
At the time, Dr Spencer, who holds a degree in botany and a PhD on aquatic fungi, was working as botany curator for the Natural History Museum. Although surprised by the call, he agreed to visit the scene to analyse the vegetation and collect samples for further study.
After submitting a report to the police, Dr Spencer had some thinking to do. “Could I do this again? Would I like to? Yes, I’m hooked already – it’s fascinating. Now, every time the phone rings in my office, I have a flutter of anticipation. Is it another case?”
Since that phone call, Dr Spencer has left the Natural History Museum and is now a self-employed forensic botanist, working with police forces and forensics companies across the UK. He estimates himself as one of around only 40 forensic botanists globally. One of the most prominent, Patricia Wiltshire, provided crucial evidence in some of the most high profile British murder cases of the last 20 years.
Murder most florid
Forensic botany can be described as the study of plants to help solve legal matters, from arson and burglary to terrorism, sexual assault and murder.
Dr Spencer’s work varies from observations in the field to analysis in the lab. As a forensic botanist, his work includes deposition scene attendance – the study of an area where a body has been found – as well as helping police interpret landscapes during missing person searches and studying vegetation fragments to link suspects to crime scenes.
“It is based upon the science of botany, the oldest science of the lot pretty much you could argue,” Dr Spencer told Laboratory News. “It is based upon pure science and the understanding of the natural world.
“I validate my observations, in the case of identification I validate the museum collections and herbarium specimens if need to. So it is verifiable – everything I do is recorded very thoroughly.”
Plant-based evidence has been used in the courtroom for at least 90 years. A famous early case is the kidnap and murder of the son of American aviator and inventor Charles Lindbergh in 1932. Evidence in the case was gathered by Arthur Koehler, a wood anatomist from the Wisconsin forestry institute. Kohler was able to identify the source of a ladder used in the kidnapping, which led to the killer’s conviction.
Koehler worked on another case in the early 1920s involving a man nicknamed the “Yule Bomber” who was convicted of setting off a homemade wooden bomb.
“Forensic botany has been around for quite some time,” Dr Spencer says. “It has been and will always be a relatively rare component - but it is underused.”
Dr Spencer benefits from an extensive knowledge of the Natural History Museum’s herbarium collection, which is estimated to catalogue more than 5 million individual species, as a means to identify clues. And with around 5,000 wild native and non-native plants growing in Britain and a variety of additional contributing growth factors such as soil types and seasonality, every single crime scene is different.
Plants can be exceptionally sensitive to humans, from the lightest of contact to the heaviest of decomposing human matter. In the case of the latter, plants grow around human remains over time and thus act as time capsules. In particular, brambles, Dr Spencer says, are “vegetable calendars”.
“I often use brambles because they are abundant, they tend to grow in places where people try to hide bodies – in woods, hedgerows, and because of the growth structure of the plants they make pretty good chronometers,” he says.
“Even though they appear kind of unruly and chaotic, growth patterns of a bramble are organised, iterative and cyclical and so they can provide you with an estimate for how long somebody has been laying on the ground or in a shallow grave.”
A decomposing human body affects factors such as growth patterns and seed dispersion to the extent that a botanist can piece together a timespan – such as by comparing the vegetation protruding from around the body with that underneath.
In the case of Dr Spencer’s very first assignment, based on regrowth patterns of surrounding Himalayan balsam plants, he was able to determine that the man in question had arrived at the deposition scene within the previous two months.
Questions remain as to how decaying human remains affect growth patterns in vegetation. What we do know is that plants are autotroph, and feed off simple compounds – sunlight, energy and water.
“The classic thing you’ll often hear probably in the wider public is ‘you can find a dead body because the plants go bananas because of all the nutrients underneath’ – that's wrong. It’s much more complicated than that.
“Human remains are biological material - complex organic compounds. We break down and we impact vegetation, bacterial communities, fungi. We are complex organic compounds as we break down, we are not yummy for plants to put it in really crude terms – we, if anything, are highly toxic.”
Human remains have very high PH and salt levels and can produce by-products such as methane, hydrogen sulphide and ammonia – meaning the surrounding vegetation dies too.
Despite a long history, there is much untapped potential in this line of work to solve crimes, and no dedicated research facilities exist in the UK.
In the US, specialist research centres known as body farms have been set up to observe how corpses – some human, donated by the recently decreased – decompose in different scenarios that emulate crime scenes, such as fires, shallow burials in woods or submerged in water.
There are only eight body farms in the world – seven in the US and one in Australia. But, if one were to be established in the UK, it could have serious benefits for forensic anthropologists and botanists.
“When you understand processes of change you can then look at timeframes and also unpick different types of damage because certain types of damage to bodies could be down to wildlife predation or it could be purposeful damage by the perpetrator,” Dr Spencer says. “So there’s a huge amount of interactions on the human remains that are best studied with [body] donors.
“Myself and many of my peers who work in the field would dearly love to have one in this country because it would be very scientifically interesting.”
Partly due to forensic botany’s low profile, a lack of funding and the current state of UK forensics, the UK is somewhat behind in the field of forensic botany. Police staff are still surprised that such a discipline even exists, Dr Spencer says, and to his knowledge, no institution in the world offers a degree in forensic botany.
If there were a greater awareness of the potential of plants to provide conclusive evidence it could ultimately secure more convictions in serious criminal cases.
“I’m very passionate about the need to connect with people on the importance of plants as a whole. Societally we’re completely and utterly blind to plants, much to our detriment, and we need to find every which way we possibly can as botanists of going ‘plants aren’t just boring green blobs’.
“There’s a huge lack of awareness in UK police forces about environmental forensics and a real training need for the discipline as a whole. Relevant staff in police forces are nearly always very interested but very rarely have the time to follow up professionally.
“They often kind of view me as the slightly weird man from London who does voodoo-y type things until I explain to them what it’s all about.”
Dr Mark Spencer’s new book, Murder Most Florid, is out now.