A major aspect of crime scene investigation is the
collection of evidence. Plants are likely not the first thing to come to mind
when considering valuable evidence for solving a murder. One probably thinks of
other types of evidence, such as blood, fingerprints, weapons, or shoe prints.
Those are examples of more commonly encountered evidence. However, forensic
botany can also provide significant information about a crime that was
committed. The anatomy, taxonomy, and ecology of plants are some features of
botanical evidence that can be analyzed. The identification of plant species
can link the suspect to the crime scene or indicate if the body was moved from
one location to another. Additionally, the time a body was buried or left at a
site can potentially be determined using plant material.
Forensic
botany involves the use of plants to aid criminal investigations. In 1992,
plant DNA was used to solve a murder investigation in Arizona. It was the first
time that plant DNA typing was legally accepted as evidence. The body of a
woman was discovered in the Arizona desert underneath a Palo Verde tree. A suspect,
Mark Bogan, was identified using a beeper found near the body. In the back of
his truck, there were seed pods from a Palo Verde tree. Could DNA analysis
match the seed pods in the back of his truck to the tree the body was found
under? Dr. T. Helentjaris set out to find the answer. A technique called
Randomly Amplified Polymorphic DNA (RAPD) was used to analyze the evidence and
a band pattern was produced. He also analyzed seed pods collected from other
Palo Verde trees throughout Maricopa County to find out if the band patterns of
the seed pods were specific to individual Palo Verde trees. He concluded that
the seed pods collected from Bogan’s truck came from the tree at the crime
scene. He testified in court, and Bogan was convicted of first degree murder.
Often,
botanical trace evidence does not have enough features, especially when the
plant material is deteriorated, to identify the genus or species of the plant,
so DNA technology is used. Dr. Robert Bever and the Bode Technology Group, Inc.
are working on creating molecular methods for analyzing botanical trace
evidence, which can be very useful for linking evidence and/or suspects to the
crime scene. Using plant systematics, many loci that aid in the identification
of plants have been characterized, which include several nuclear (18S, ITS1,
ITS2) and chloroplast (rbcL, atpB, ndhF) genes. A DNA extraction, cloning, and
sequencing procedure for identifying plants has been created by the Bode
Technology Group, Inc. using some of those genes. Applying these methods, many
plant species have been identified from physical evidence, such as algae,
evergreens, and flowering herbs, shrubs, and trees. Some plants are located in
very specific areas in which botanical trace evidence could be extremely
valuable for establishing linkage.
I
provided one example of how plant material can be used as forensic evidence,
but the attached article contains many more cases that exemplify the impact botanical
evidence can have in solving crimes. Many of these investigations would likely
not have been solved without the collection of plant materials as evidence. This
emphasizes the importance of considering all types of items and materials as
evidence because the seemingly smallest piece of evidence could be the key to
solving the crime. Hopefully more attention will be given to this type of
evidence when analyzing crime scenes given the impact it could have on the
investigation.
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