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TREES, PLEASE! Tattle Tree

Photo credit: Wikimedia Commons.
A Palo Verde tree is lit up by the sunset near Quartzsite, AZ.

By Tim Clancy.

For a few dollars you can send a DNA sample to any one of a number of companies that will do an analysis of your sample and provide you with information about your heritage. PBS has a show dedicated to the use of DNA to uncover both famous and infamous connections to the past of contemporary celebrities. Sometimes the DNA dispels myths and family legends of these high-profile individuals.

DNA has been used to exonerate accused individuals as well and one criminal used DNA from other people to confuse investigators. For most of us DNA and its use in criminal investigations relates to human DNA.

It turns out that plants can also be differentiated by the use of DNA as well. A young woman was found dead in a secluded area outside of Phoenix. During a search of the crime scene investigators heard a beeping sound and recovered a pager (remember those?). The pager led the detectives to an individual. Upon interviewing the man detectives noticed that he had scratches on his face and were hopeful that the deceased had scratched his face and would have some of the man's DNA under her fingernails. It was not to be and that lead turned out to be unfruitful. A through search of the suspect's truck provided no clues either (He had cleaned his truck after his deed was committed). However, while collecting evidence from the truck seed pods were collected and bagged.

While at the crime scene a detective noticed that there were trees (Palo Verde) that had similar looking seed pods. This led to the suggestion of using DNA to prove the man was at the scene despite his protestations of not ever having been there. A detective called around the country looking for someone to do the analysis and was met with skepticism on 14 calls. On the 15th call to a geneticist 100 miles away he found someone at the University of Arizona who agreed the task.

The crime scene was near a small grove of the trees so prosecutors provided samples from multiple trees and sure enough the geneticist was able to identify an individual tree the seed pods came from. The prosecutor was concerned that such a small sample would not convince a jury (This was 2 years before the O.J. Simpson trial, remember that?). So, in an effort to bolster his case and prove that trees could be individually be distinguished by DNA decided to conduct a test using 100 random samples.

Photo credit: Tim Clancy.
Who's your daddy?

Once again the geneticist went to work and did indeed find that 99 of the 100 samples were genetically distinct. He did however have some bad news in that one of the samples came back as a perfect match to the tree originally identified as the one at the crime scene. This was music to the prosecutor’s ears as he had unbeknownst to the geneticist included a sample from the original tree as a test! He was now confident that even though there were thousands of Palo Verde trees in and around Phoenix he could show a jury that DNA was indeed individual to plants as well as humans.

The murder suspect was convicted and sentenced to life in prison. This was the first time in history that plant DNA was used to convict a murderer. Now that's planted evidence.


Contributor Tim Clancy is an International Society of Arboriculture Certified Arborist

No. WE-0806A and Tree Risk Assessment Qualified.


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