Crime Scene Botanics, the forensic side of botany

Planting Clues should not only appeal to the general reader, but will also serve well as a textbook for an undergraduate course on forensic botany.
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Planting Clues: How plants solve crimes by David J Gibson, 2022. Oxford University Press.

First things first [and spoiler alert], plants do not solve crimes.* People solve crimes, although – as Planting Clues by David Gibson [which book is here appraised] shows so convincingly – plants may provide evidence that can help with that.


The book begins with a Preface. That’s always a good place to begin reading a book since here it has important things to say about the author’s goal in writing the tome, and provides this all-important definition: “Forensic botany is concerned with the use of plants as evidence in legal settings, in both criminal and civil cases” (pp. vii-viii). The Preface also tells us that the book “interleaves famous legal cases with aspects of botany that help solve crimes. I present these ideas in the context of botanical cases, focusing on the admissibility and scientific validity of plant-based evidence presented to the legal profession” (p. x). The 198 pages of main text** are spread over 7 chapters – each written as continuous narrative without sub-headings – and a concluding 2.5 page ‘coda’, with sources indicated by super-scripted numbers in-text. Thereafter we have a Glossary, Endnotes, and two Indexes.

The Glossary – of approx. 4.5 pages – “provides a brief explanation of some of the forensic chemical and molecular methods mentioned in the text” (p. 199). The Endnotes group the numbered sources by chapter number [a really useful amendment in future editions would be to provide the chapter title as well to make it easier to leaf through these 21 pages to find the correct note]. Sources cited are a very good mix of web resources, books, legal cases, and scientific articles. Approx. 160 of those latter references are dated post-2010 – including almost all of the sources for Chapters 5 and 6 – which makes Planting Clues a very up-to-date book.

The General Index – 2-columned, 6 pages’ worth – is accompanied by the Plant, Algae and Fungal Species Index [Gibson uses ‘plants’ as a “catch-all to include plants (in the strictest sense, including algae) and fungi together” (p. x)]. Although only approx. 3.33 pages long, this 2-columned listing is an impressive catalogue of plants with forensic relevance, with entries in alphabetical order of scientific name (but also stating the common name). Running from Abies lasiocarpa (subalpine fir) to Zea mays (maize), via Dalbergia spp. (rosewood) (HG Richter et al.), Hantzchia spp. (diatom) [which should be spelt Hantzschia?], and Psilocybe semilanceata (magic mushroom) (Adrastos Omissi), it really emphasises the botany in forensic botany.

Planting Clues is illustrated, but the quality of the 11 black-and-white figures reproduced on the normal paper for the book are of variable quality – especially the photographs. However, the quality of the five colour plates – grouped together on glossy paper between pages 114 and 115 – is consistent and very good. A scale bar would be useful so readers could appreciate the size of the diatoms in Plate 3 – but it’s nice to see the magnification usefully stated re pollen in Plate 2.


Planting Clues’ intended readership is indicated by the inside front cover of the dust jacket which states: “This book should fascinate plant lovers and readers of true crime alike”. To which categories one might add – somewhat mischievously – and those thinking of perpetrating crimes with a view to eliminating plant evidence of their misdemeanours. However, as Gibson makes quite clear with the numerous case-studies, it’s almost impossible to eliminate entirely botanical evidence. Hopefully, therefore, this book should act as a deterrent to any would-be wrong-doers.


Indications of sources for the numerous facts stated in Planting Clues are included within the text as super-scripted numbers. But, rather than cite those at the beginning of the text about a particular case or whatever, they tend to be provided at the end of the relevant paragraph(s), e.g. at the conclusion of the third paragraph about ‘the Taipei case’ (pp. 60/1). However, even though there are lots of references, in many areas either the source stated doesn’t cover all of the points made, or a statement may be completely unsourced. Their omission is always disappointing in a fact-based plant biology text, but especially so in a book whose main theme is the importance of evidence. In keeping with that need to provide evidence, here are some examples of facts for which a source(s) is needed: the statements about ring- and diffuse-porous wood (p. 8); the technical details re Sphagnum (p. 38), information on the herbicidal properties of 2,4-D (p. 46); the number of species [“more than 32,000”] in the Asteraceae (p. 49); the behaviour of the pyloric sphincter upon death (p. 52); that a body adds 2.6 kg of nitrogen to the soil (p. 71), the properties of plant poisons (pp. 140/1), and the numerous facts stated about poisons in ancient Rome, the Middle Ages [featuring an explanation for the tradition of drinkers ‘clinking glasses’…], and culminating in mention of 20th century serial-killer Dr Harold Shipman (pp. 144-146). Otherwise, the level of statement-sourcing is pretty good – as should be expected from Gibson’s academic teaching credentials.

Personal take on book…

Planting Clues provides some quite personal anecdotal material, lots of plant biology, forensic science (including important information about the nature and admissibility of evidence), and musings on plant blindness. Although it includes lots of technical material, it’s delivered in a way that should be accessible to non-specialists, non-botanists, and the interested general reader alike. Indeed, generally, it’s very well-written and contains much of educational value. Full of fascinating forensic facts – as you’d expect – it makes an excellent case [no pun intended…] for the value of plant-derived evidence in legal investigations. Usefully, it doesn’t just focus on ‘proper’ plants but also gives a really good ‘shout-out’ for diatoms and fungi.

Hopefully, the comments that follow will give a flavour of the book’s contents and coverage.

Chap. 1 “A tree never lies” has an important focus upon the 1932 ‘Lindbergh kidnapping’ case and the important part played by tree anatomy in forensics. I think it’s an unwritten rule that this infamous case has to be mentioned in every piece of writing about forensic botany. But, although I had some familiarity with the botanical – specifically, wood anatomical – features of that investigation, the level of detail provided by Gibson provided a much-appreciated in-depth look at that particular case. Pleasingly – and largely because of the way it’s presented – that level of intricate detail was easy to assimilate [and I learnt about the so-called Lindbergh Law, the astounding fact that kidnapping was only made a federal offence in the USA as a result of this case, that there was an ‘Australian Lindbergh case’ in 1960 (which is covered in Chap. 4), and that kidnapping wasn’t even an offence in Australia until remedied by parliament in 1961]. Furthermore, providing that degree of detailed analysis underlined not only the value of botanical evidence in legal cases, but also emphasised the great deal of care that is necessary to ensure that the such evidence is robust and its examination thoroughly carried out, by appropriate specialists.

Chap. 2 “Everything that’s touched” contains fascinating information about the “Sherlock Holmes of France” (p. 23), Edmond Locard, and his pioneering use of forensic evidence in the early 20th Century. In particular it introduces us to Locard’s now-famous ‘exchange principle’, which is still used in 21st century forensic investigations.

Chap. 3 “Getting caught up” gives probably more information than you’d like on the evidentiary value of plant material in the stomach contents of the deceased. Curiously, there was no mention here of ‘the Adam case’ – an unsolved murder of a young boy in London – in which staff at Kew played an important role (Sarah Bell) in the forensic botanical examination of Adam’s last meal.

Chap. 4 “Every particle tells a story” looks at the role of small botanics generally, and includes the always-fascinating notion that diatoms are inhaled by drowning people and transported to the bone marrow (Anthony Peabody; Ajay Singh Rana & P Varma, Int J Forens Sci 2019, 4(1): 000160; doi: 10.23880/ijfsc-16000160). The UK’s infamous ‘Soham murders’ case (Frances Kindon & Kaitlin Easton) is also covered in this chapter.

Chap. 5 “It’s in the genes” provides lots of information about the molecular side of things – especially the role of plant DNA in criminal investigations. Accordingly, the USA’s famous ‘Maricopa case’ (Carol Kaesuk Yoon; HemRaj Singh) gets a very good airing, as do investigations into contamination of organic crops by GM crops. Although it’s probably the most technical of the book’s chapters, with Gibson’s accessible writing style – and by reference to the Glossary – it’s understandable, and takes forensic botany to the ultimate level of sophistication.

Chap. 6 “A forensic pharmacopoeia” deals with plant(and fungal)-derived toxins. It was one of the most fascinating chapters presenting not so much a ‘whodunnit’ but more of a ‘whatdunnit’ in considering a range of natural ‘murderous molecules’.

Chap. 7 “Hiding in plain sight” provides an important look at the role played by forensic botany with respect to the lucrative international trade in rare and protected plants and plant products. This chapter underlines the fact that botanical evidence is not only important in crimes against people, but also crimes against the planet in which CITES-listed species and their resources are plundered and Earth’s biodiversity consequently depleted to the detriment of all.

The narrative side of the book is completed not by a chapter, but by a coda that deals with ‘plant blindness’.*** Although any reader who gets to this stage of the book must be all too aware of the importance of plants in forensics, it is Gibson’s experience – and that of “the most prominent current forensic botanists” (p. viii) – that an appreciation of the value of plants in forensics is often lacking. Whether this plea for more-botanically-astute individuals concerned with law enforcement and crime-solving will be heeded is something for the future, but it’s worthwhile making.

Another relatively-recently-published book about forensic botany is Mark Spencer’s book Murder Most Florid. Spencer’s book is much more of a personal reflection on the work of a forensic botanist by one who is a practitioner of the science. Gibson’s tome has much more of the case-study, textbook quality about it – as befits its being written by one who teaches the subject. Both books are really great reads – but for different reasons.

Planting Clues gives a much-appreciated – invaluable, and probably long-overdue – insight into forensic botany. But, it’s not all high-profile murder cases that Gibson covers, there are plenty of less ‘glamorous’ ones including policing the trade in endangered plants and their products. This latter area also highlights the need for botanical experts to examine the items being traded – especially those who are taxonomically-trained to ensure the true identity of the plants involved. Which contributes to Gibson’s plea in the final text section for more botanists (and therefore more botanically-relevant teaching in universities, etc.), and more botanically-aware members of the law-enforcement community.

When developing my own forensic botany lecture in 2002 the main problem I had was getting enough examples: Gibson’s book would certainly have solved that problem. And that use is underlined by the publisher’s web-site where Planting Clues is included amongst their ‘academic’ category of titles. But don’t be put-off by the academic categorisation. Although Gibson says that he found writing an engaging text that non-botanists and non-scientists would enjoy reading was quite different to researching the scientific content of the material provided, he has done a great job; Planting Clues is both engaging and enjoyable to read.


Planting Clues by David Gibson is a great book that’s well-written with plenty of examples of the value of botany and plants (and algae and fungi…) to forensic investigations. Written in a very accessible way, Planting Clues should not only appeal to the general reader, but will also serve well as a textbook for an undergraduate course on forensic botany [which is how the idea for the book began], and is a most welcome addition to the literature on plant-based forensics.****

* The book’s sub-title is therefore a little misleading. I also have a problem with the book’s title. Although I recognise its value as a botanically-related pun, planting clues sounds like one is placing evidence in a deliberate attempt to mislead the police or whoever, or to implicate AN Other in the crime [see also here, and here]. Since the book’s premise is that plants can provide evidence that may help to correctly solve a crime, quite the opposite meaning is actually intended.

** Hearteningly, the text appears to be generally error-free. The only issue I noted relates to “ground ivy (Hedera helix)” (on page 96). The plant referred to sounds like common ivy, Hedera helix when one reads other statements in connection with the mentioned plant. Ground ivy is the common name of Glechoma hederacea.

*** For some sort of completeness, and because the book was probably completed too soon to allow citation of articles such as those by Sarah Jose et al. (Plants People Planet 1: 169-172, 2019;, Sandra Knapp (Plants People Planet 1: 164-168, 2019;, and Kathryn Parsley (Plants People Planet 2: 598-601, 2020;, they are included here for those who desire to know a little more about the phenomenon known as plant blindness/plant awareness disparity.

**** I don’t know what literature is required reading for those undertaking instruction in forensic investigations, but it would be nice to think that Planting Clues would be added to that list.

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