Forensic Botany - an under-used source of potential evidence

Forensic Botany is the application of plant science to the investigation of criminal and civil cases.  The value of using plant remains as evidence lies in the fact that they can be found almost everywhere.

 

But despite its proven value, forensic botany is not part of mainstream forensics.  Its practitioners tend to work in university departments rather than forensics laboratories.

 

A major obstacle to the routine use of botanical evidence has been the lack of trained specialists. 

 

As a degree subject, botany began to wane in popularity in the 1970s. (There were only six of us majoring in botany at my university in 1974).  The courses were viewed as old-fashioned, with their traditional content of plant morphology, anatomy, and systematics.  Instead, students flocked to those courses offering the study of plants at the molecular level.

 

Today, forensic botany encompasses expertise in both traditional plant science and molecular biology.  As well as the interpretation of botanical evidence left at a crime scene, forensic botanists are able to identify individual plants from an analysis of their DNA.

 

So how can forensic botany help an investigation?  Here are a few examples.  The list is not exhaustive, as I am planning on re-visiting this subject in future blogs.

 

• Seeds can be carried in trousers turn-ups (cuffs), thereby potentially linking an individual wth a specific location.

• The identification of vegetable matter in stomach contents can provide evidence of a victim's last meal.

• Pollen types that occur together in a crime scene sample can show where somebody or something has been.  This can be very specific evidence.  It can indicate geographical origin in instances where certain plants only occur in particular areas in certain combinations.


• From the use of plant growth patterns and habitat details, it is possible to infer how long skeletal remains have been present in a particular location.
 
• DNA analysis of fragments of marijuana can establish distribution patterns and links between growers.

Here is a short video that shows how forensic botany can be used to determine that a body has been moved.  The video also shows how a perpetrator can be linked to a scene or victim by plant material.

 

Forensic botany is an important tool for the location of clandestine graves.  Here is an account of a double homicide where pollen evidence helped police find the graves of the victims.

 

On 6th December 1994, Roger Severs was found guilty of the murder of his parents, Derek and Eileen Severs.  He was sentenced to two terms of life imprisonment.

 

Roger Severs was unemployed and lived with his parents at their home in Hambleton, Leicestershire, UK.  One evening, Severs returned home drunk.  His mother was at home, alone.  Severs asked her for money, probably to fund his latest business idea.  When she refused, he flew into a rage and battered her to death with a steak mallet.

 

Later on, when his father came home, Severs beat him to death as well.

 

Derek and Eileen Severs were comfortably off and Roger Severs could expect a good inheritance.  They had been actively involved in their local community and had many friends.  After a week of missed appointments - which was totally out of character - and despite being told by Severs that his parents were on holiday, their friends became increasingly worried and called the police.

 

When the police arrived at the couple's bungalow, they found it in a state of disarray.  In particular, they noticed that the carpets had been removed from two of the rooms.  Severs was adamant that his parents were on holday.

 

However, the police investigations revealed Derek and Eileen had not made any travel arrangements.  Instead, it was clear that they had no intention of going on holiday, as they had made a number of appointments to see friends when they were supposedly away.

 

Two days later, the police arrested Severs and a forensic examination of his parents' bungalow was carried out.

 

Scenes of Crime Officers (SOCOs) found blood spatter in the bathroom, indicating that a violent attack had taken place.  Blood traces near the garage were indicative of a second attack. 

 

The SOCOs also found a trail of yellow fibres with a 'rolled' appearance, suggesting that something heavy had been dragged over the carpet.

 

But where were the bodies? 

 

It was possible that they had been taken to another location.  Derek and Eileen's car was extremely muddy, both inside and out.  The SOCOs took mud samples from the wheel arches and footwells of the car.

 

A detailed analysis of the mud showed that it had been accumulated recently and contained quartz, calcite, ironstone, chert and coated road stone.  A forensic geologist concluded that this mineral composition indicated that the mud had come from an unmade road (trail) in East Leicestershire.

 

A further analysis of the mud revealed several types of pollen grains, in particular, oak, birch and horse chestnut.  The density of the oak pollen suggested that the car had been taken to a site next to an oak tree and also showed the direction in which it had been parked.

 

In order to locate the likely grave site of Derek and Eileen, Professor Tony Brown of Leicester University, a forensic botanist specialising in palynology (pollen analysis), collaborated with ecologists from the Leicestershire and Rutland Wildlife Trust, who possessed good knowledge of the tree species in the surrounding countryside.  Between them, they reduced the search area from a 40km radius to five likely woodlands.  Derek and Eileen's bodies were discovered at the second site that was searched.

Eileen was wrapped in a yellow blanket, hence the trail of yellow fibres found by the SOCOs. 

The soil on top of the bodies came from Derek and Eileen's garden.  Severs had first of all placed the bodies in a shallow dip.  He then drove to and from their bungalow with bags of soil. He emptied the bags on top of the bodies and disguised the grave with leaves and twigs.

The SOCOs found a 'To do' list which Severs had written after the murders.  One of the tasks was to clean the car. Fortunately, he was arrested before he had completed that particular chore.

 

There are lots of interesting cases where plant evidence is important, so, as I mentioned earlier, I'll re-visit this subject in other blogs.  In the meantime, I hope this blog has 'planted' some new ideas that you can use in your writing. 

 

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